feat: initial commit - Phase 1 & 2 core features

backend/.venv/lib/python3.9/site-packages/sklearn/compose/__init__.py

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+"""Meta-estimators for building composite models with transformers
+
+In addition to its current contents, this module will eventually be home to
+refurbished versions of Pipeline and FeatureUnion.
+
+"""
+
+from ._column_transformer import (
+    ColumnTransformer,
+    make_column_selector,
+    make_column_transformer,
+)
+from ._target import TransformedTargetRegressor
+
+__all__ = [
+    "ColumnTransformer",
+    "make_column_transformer",
+    "TransformedTargetRegressor",
+    "make_column_selector",
+]

backend/.venv/lib/python3.9/site-packages/sklearn/compose/_target.py

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+# Authors: Andreas Mueller <andreas.mueller@columbia.edu>
+#          Guillaume Lemaitre <guillaume.lemaitre@inria.fr>
+# License: BSD 3 clause
+
+import warnings
+
+import numpy as np
+
+from ..base import BaseEstimator, RegressorMixin, _fit_context, clone
+from ..exceptions import NotFittedError
+from ..preprocessing import FunctionTransformer
+from ..utils import _safe_indexing, check_array
+from ..utils._param_validation import HasMethods
+from ..utils._tags import _safe_tags
+from ..utils.metadata_routing import (
+    _raise_for_unsupported_routing,
+    _RoutingNotSupportedMixin,
+)
+from ..utils.validation import check_is_fitted
+
+__all__ = ["TransformedTargetRegressor"]
+
+
+class TransformedTargetRegressor(
+    _RoutingNotSupportedMixin, RegressorMixin, BaseEstimator
+):
+    """Meta-estimator to regress on a transformed target.
+
+    Useful for applying a non-linear transformation to the target `y` in
+    regression problems. This transformation can be given as a Transformer
+    such as the :class:`~sklearn.preprocessing.QuantileTransformer` or as a
+    function and its inverse such as `np.log` and `np.exp`.
+
+    The computation during :meth:`fit` is::
+
+        regressor.fit(X, func(y))
+
+    or::
+
+        regressor.fit(X, transformer.transform(y))
+
+    The computation during :meth:`predict` is::
+
+        inverse_func(regressor.predict(X))
+
+    or::
+
+        transformer.inverse_transform(regressor.predict(X))
+
+    Read more in the :ref:`User Guide <transformed_target_regressor>`.
+
+    .. versionadded:: 0.20
+
+    Parameters
+    ----------
+    regressor : object, default=None
+        Regressor object such as derived from
+        :class:`~sklearn.base.RegressorMixin`. This regressor will
+        automatically be cloned each time prior to fitting. If `regressor is
+        None`, :class:`~sklearn.linear_model.LinearRegression` is created and used.
+
+    transformer : object, default=None
+        Estimator object such as derived from
+        :class:`~sklearn.base.TransformerMixin`. Cannot be set at the same time
+        as `func` and `inverse_func`. If `transformer is None` as well as
+        `func` and `inverse_func`, the transformer will be an identity
+        transformer. Note that the transformer will be cloned during fitting.
+        Also, the transformer is restricting `y` to be a numpy array.
+
+    func : function, default=None
+        Function to apply to `y` before passing to :meth:`fit`. Cannot be set
+        at the same time as `transformer`. If `func is None`, the function used will be
+        the identity function. If `func` is set, `inverse_func` also needs to be
+        provided. The function needs to return a 2-dimensional array.
+
+    inverse_func : function, default=None
+        Function to apply to the prediction of the regressor. Cannot be set at
+        the same time as `transformer`. The inverse function is used to return
+        predictions to the same space of the original training labels. If
+        `inverse_func` is set, `func` also needs to be provided. The inverse
+        function needs to return a 2-dimensional array.
+
+    check_inverse : bool, default=True
+        Whether to check that `transform` followed by `inverse_transform`
+        or `func` followed by `inverse_func` leads to the original targets.
+
+    Attributes
+    ----------
+    regressor_ : object
+        Fitted regressor.
+
+    transformer_ : object
+        Transformer used in :meth:`fit` and :meth:`predict`.
+
+    n_features_in_ : int
+        Number of features seen during :term:`fit`. Only defined if the
+        underlying regressor exposes such an attribute when fit.
+
+        .. versionadded:: 0.24
+
+    feature_names_in_ : ndarray of shape (`n_features_in_`,)
+        Names of features seen during :term:`fit`. Defined only when `X`
+        has feature names that are all strings.
+
+        .. versionadded:: 1.0
+
+    See Also
+    --------
+    sklearn.preprocessing.FunctionTransformer : Construct a transformer from an
+        arbitrary callable.
+
+    Notes
+    -----
+    Internally, the target `y` is always converted into a 2-dimensional array
+    to be used by scikit-learn transformers. At the time of prediction, the
+    output will be reshaped to a have the same number of dimensions as `y`.
+
+    Examples
+    --------
+    >>> import numpy as np
+    >>> from sklearn.linear_model import LinearRegression
+    >>> from sklearn.compose import TransformedTargetRegressor
+    >>> tt = TransformedTargetRegressor(regressor=LinearRegression(),
+    ...                                 func=np.log, inverse_func=np.exp)
+    >>> X = np.arange(4).reshape(-1, 1)
+    >>> y = np.exp(2 * X).ravel()
+    >>> tt.fit(X, y)
+    TransformedTargetRegressor(...)
+    >>> tt.score(X, y)
+    1.0
+    >>> tt.regressor_.coef_
+    array([2.])
+
+    For a more detailed example use case refer to
+    :ref:`sphx_glr_auto_examples_compose_plot_transformed_target.py`.
+    """
+
+    _parameter_constraints: dict = {
+        "regressor": [HasMethods(["fit", "predict"]), None],
+        "transformer": [HasMethods("transform"), None],
+        "func": [callable, None],
+        "inverse_func": [callable, None],
+        "check_inverse": ["boolean"],
+    }
+
+    def __init__(
+        self,
+        regressor=None,
+        *,
+        transformer=None,
+        func=None,
+        inverse_func=None,
+        check_inverse=True,
+    ):
+        self.regressor = regressor
+        self.transformer = transformer
+        self.func = func
+        self.inverse_func = inverse_func
+        self.check_inverse = check_inverse
+
+    def _fit_transformer(self, y):
+        """Check transformer and fit transformer.
+
+        Create the default transformer, fit it and make additional inverse
+        check on a subset (optional).
+
+        """
+        if self.transformer is not None and (
+            self.func is not None or self.inverse_func is not None
+        ):
+            raise ValueError(
+                "'transformer' and functions 'func'/'inverse_func' cannot both be set."
+            )
+        elif self.transformer is not None:
+            self.transformer_ = clone(self.transformer)
+        else:
+            if (self.func is not None and self.inverse_func is None) or (
+                self.func is None and self.inverse_func is not None
+            ):
+                lacking_param, existing_param = (
+                    ("func", "inverse_func")
+                    if self.func is None
+                    else ("inverse_func", "func")
+                )
+                raise ValueError(
+                    f"When '{existing_param}' is provided, '{lacking_param}' must also"
+                    f" be provided. If {lacking_param} is supposed to be the default,"
+                    " you need to explicitly pass it the identity function."
+                )
+            self.transformer_ = FunctionTransformer(
+                func=self.func,
+                inverse_func=self.inverse_func,
+                validate=True,
+                check_inverse=self.check_inverse,
+            )
+        # XXX: sample_weight is not currently passed to the
+        # transformer. However, if transformer starts using sample_weight, the
+        # code should be modified accordingly. At the time to consider the
+        # sample_prop feature, it is also a good use case to be considered.
+        self.transformer_.fit(y)
+        if self.check_inverse:
+            idx_selected = slice(None, None, max(1, y.shape[0] // 10))
+            y_sel = _safe_indexing(y, idx_selected)
+            y_sel_t = self.transformer_.transform(y_sel)
+            if not np.allclose(y_sel, self.transformer_.inverse_transform(y_sel_t)):
+                warnings.warn(
+                    (
+                        "The provided functions or transformer are"
+                        " not strictly inverse of each other. If"
+                        " you are sure you want to proceed regardless"
+                        ", set 'check_inverse=False'"
+                    ),
+                    UserWarning,
+                )
+
+    @_fit_context(
+        # TransformedTargetRegressor.regressor/transformer are not validated yet.
+        prefer_skip_nested_validation=False
+    )
+    def fit(self, X, y, **fit_params):
+        """Fit the model according to the given training data.
+
+        Parameters
+        ----------
+        X : {array-like, sparse matrix} of shape (n_samples, n_features)
+            Training vector, where `n_samples` is the number of samples and
+            `n_features` is the number of features.
+
+        y : array-like of shape (n_samples,)
+            Target values.
+
+        **fit_params : dict
+            Parameters passed to the `fit` method of the underlying
+            regressor.
+
+        Returns
+        -------
+        self : object
+            Fitted estimator.
+        """
+        _raise_for_unsupported_routing(self, "fit", **fit_params)
+        if y is None:
+            raise ValueError(
+                f"This {self.__class__.__name__} estimator "
+                "requires y to be passed, but the target y is None."
+            )
+        y = check_array(
+            y,
+            input_name="y",
+            accept_sparse=False,
+            force_all_finite=True,
+            ensure_2d=False,
+            dtype="numeric",
+            allow_nd=True,
+        )
+
+        # store the number of dimension of the target to predict an array of
+        # similar shape at predict
+        self._training_dim = y.ndim
+
+        # transformers are designed to modify X which is 2d dimensional, we
+        # need to modify y accordingly.
+        if y.ndim == 1:
+            y_2d = y.reshape(-1, 1)
+        else:
+            y_2d = y
+        self._fit_transformer(y_2d)
+
+        # transform y and convert back to 1d array if needed
+        y_trans = self.transformer_.transform(y_2d)
+        # FIXME: a FunctionTransformer can return a 1D array even when validate
+        # is set to True. Therefore, we need to check the number of dimension
+        # first.
+        if y_trans.ndim == 2 and y_trans.shape[1] == 1:
+            y_trans = y_trans.squeeze(axis=1)
+
+        if self.regressor is None:
+            from ..linear_model import LinearRegression
+
+            self.regressor_ = LinearRegression()
+        else:
+            self.regressor_ = clone(self.regressor)
+
+        self.regressor_.fit(X, y_trans, **fit_params)
+
+        if hasattr(self.regressor_, "feature_names_in_"):
+            self.feature_names_in_ = self.regressor_.feature_names_in_
+
+        return self
+
+    def predict(self, X, **predict_params):
+        """Predict using the base regressor, applying inverse.
+
+        The regressor is used to predict and the `inverse_func` or
+        `inverse_transform` is applied before returning the prediction.
+
+        Parameters
+        ----------
+        X : {array-like, sparse matrix} of shape (n_samples, n_features)
+            Samples.
+
+        **predict_params : dict of str -> object
+            Parameters passed to the `predict` method of the underlying
+            regressor.
+
+        Returns
+        -------
+        y_hat : ndarray of shape (n_samples,)
+            Predicted values.
+        """
+        check_is_fitted(self)
+        pred = self.regressor_.predict(X, **predict_params)
+        if pred.ndim == 1:
+            pred_trans = self.transformer_.inverse_transform(pred.reshape(-1, 1))
+        else:
+            pred_trans = self.transformer_.inverse_transform(pred)
+        if (
+            self._training_dim == 1
+            and pred_trans.ndim == 2
+            and pred_trans.shape[1] == 1
+        ):
+            pred_trans = pred_trans.squeeze(axis=1)
+
+        return pred_trans
+
+    def _more_tags(self):
+        regressor = self.regressor
+        if regressor is None:
+            from ..linear_model import LinearRegression
+
+            regressor = LinearRegression()
+
+        return {
+            "poor_score": True,
+            "multioutput": _safe_tags(regressor, key="multioutput"),
+        }
+
+    @property
+    def n_features_in_(self):
+        """Number of features seen during :term:`fit`."""
+        # For consistency with other estimators we raise a AttributeError so
+        # that hasattr() returns False the estimator isn't fitted.
+        try:
+            check_is_fitted(self)
+        except NotFittedError as nfe:
+            raise AttributeError(
+                "{} object has no n_features_in_ attribute.".format(
+                    self.__class__.__name__
+                )
+            ) from nfe
+
+        return self.regressor_.n_features_in_

backend/.venv/lib/python3.9/site-packages/sklearn/compose/tests/test_target.py

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+import numpy as np
+import pytest
+
+from sklearn import datasets
+from sklearn.base import BaseEstimator, TransformerMixin, clone
+from sklearn.compose import TransformedTargetRegressor
+from sklearn.dummy import DummyRegressor
+from sklearn.linear_model import LinearRegression, OrthogonalMatchingPursuit
+from sklearn.pipeline import Pipeline
+from sklearn.preprocessing import FunctionTransformer, StandardScaler
+from sklearn.utils._testing import assert_allclose, assert_no_warnings
+
+friedman = datasets.make_friedman1(random_state=0)
+
+
+def test_transform_target_regressor_error():
+    X, y = friedman
+    # provide a transformer and functions at the same time
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(),
+        transformer=StandardScaler(),
+        func=np.exp,
+        inverse_func=np.log,
+    )
+    with pytest.raises(
+        ValueError,
+        match="'transformer' and functions 'func'/'inverse_func' cannot both be set.",
+    ):
+        regr.fit(X, y)
+    # fit with sample_weight with a regressor which does not support it
+    sample_weight = np.ones((y.shape[0],))
+    regr = TransformedTargetRegressor(
+        regressor=OrthogonalMatchingPursuit(), transformer=StandardScaler()
+    )
+    with pytest.raises(
+        TypeError,
+        match=r"fit\(\) got an unexpected " "keyword argument 'sample_weight'",
+    ):
+        regr.fit(X, y, sample_weight=sample_weight)
+
+    # one of (func, inverse_func) is given but the other one is not
+    regr = TransformedTargetRegressor(func=np.exp)
+    with pytest.raises(
+        ValueError,
+        match="When 'func' is provided, 'inverse_func' must also be provided",
+    ):
+        regr.fit(X, y)
+
+    regr = TransformedTargetRegressor(inverse_func=np.log)
+    with pytest.raises(
+        ValueError,
+        match="When 'inverse_func' is provided, 'func' must also be provided",
+    ):
+        regr.fit(X, y)
+
+
+def test_transform_target_regressor_invertible():
+    X, y = friedman
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(),
+        func=np.sqrt,
+        inverse_func=np.log,
+        check_inverse=True,
+    )
+    with pytest.warns(
+        UserWarning,
+        match=(
+            "The provided functions or"
+            " transformer are not strictly inverse of each other."
+        ),
+    ):
+        regr.fit(X, y)
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(), func=np.sqrt, inverse_func=np.log
+    )
+    regr.set_params(check_inverse=False)
+    assert_no_warnings(regr.fit, X, y)
+
+
+def _check_standard_scaled(y, y_pred):
+    y_mean = np.mean(y, axis=0)
+    y_std = np.std(y, axis=0)
+    assert_allclose((y - y_mean) / y_std, y_pred)
+
+
+def _check_shifted_by_one(y, y_pred):
+    assert_allclose(y + 1, y_pred)
+
+
+def test_transform_target_regressor_functions():
+    X, y = friedman
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(), func=np.log, inverse_func=np.exp
+    )
+    y_pred = regr.fit(X, y).predict(X)
+    # check the transformer output
+    y_tran = regr.transformer_.transform(y.reshape(-1, 1)).squeeze()
+    assert_allclose(np.log(y), y_tran)
+    assert_allclose(
+        y, regr.transformer_.inverse_transform(y_tran.reshape(-1, 1)).squeeze()
+    )
+    assert y.shape == y_pred.shape
+    assert_allclose(y_pred, regr.inverse_func(regr.regressor_.predict(X)))
+    # check the regressor output
+    lr = LinearRegression().fit(X, regr.func(y))
+    assert_allclose(regr.regressor_.coef_.ravel(), lr.coef_.ravel())
+
+
+def test_transform_target_regressor_functions_multioutput():
+    X = friedman[0]
+    y = np.vstack((friedman[1], friedman[1] ** 2 + 1)).T
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(), func=np.log, inverse_func=np.exp
+    )
+    y_pred = regr.fit(X, y).predict(X)
+    # check the transformer output
+    y_tran = regr.transformer_.transform(y)
+    assert_allclose(np.log(y), y_tran)
+    assert_allclose(y, regr.transformer_.inverse_transform(y_tran))
+    assert y.shape == y_pred.shape
+    assert_allclose(y_pred, regr.inverse_func(regr.regressor_.predict(X)))
+    # check the regressor output
+    lr = LinearRegression().fit(X, regr.func(y))
+    assert_allclose(regr.regressor_.coef_.ravel(), lr.coef_.ravel())
+
+
+@pytest.mark.parametrize(
+    "X,y", [friedman, (friedman[0], np.vstack((friedman[1], friedman[1] ** 2 + 1)).T)]
+)
+def test_transform_target_regressor_1d_transformer(X, y):
+    # All transformer in scikit-learn expect 2D data. FunctionTransformer with
+    # validate=False lift this constraint without checking that the input is a
+    # 2D vector. We check the consistency of the data shape using a 1D and 2D y
+    # array.
+    transformer = FunctionTransformer(
+        func=lambda x: x + 1, inverse_func=lambda x: x - 1
+    )
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(), transformer=transformer
+    )
+    y_pred = regr.fit(X, y).predict(X)
+    assert y.shape == y_pred.shape
+    # consistency forward transform
+    y_tran = regr.transformer_.transform(y)
+    _check_shifted_by_one(y, y_tran)
+    assert y.shape == y_pred.shape
+    # consistency inverse transform
+    assert_allclose(y, regr.transformer_.inverse_transform(y_tran).squeeze())
+    # consistency of the regressor
+    lr = LinearRegression()
+    transformer2 = clone(transformer)
+    lr.fit(X, transformer2.fit_transform(y))
+    y_lr_pred = lr.predict(X)
+    assert_allclose(y_pred, transformer2.inverse_transform(y_lr_pred))
+    assert_allclose(regr.regressor_.coef_, lr.coef_)
+
+
+@pytest.mark.parametrize(
+    "X,y", [friedman, (friedman[0], np.vstack((friedman[1], friedman[1] ** 2 + 1)).T)]
+)
+def test_transform_target_regressor_2d_transformer(X, y):
+    # Check consistency with transformer accepting only 2D array and a 1D/2D y
+    # array.
+    transformer = StandardScaler()
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(), transformer=transformer
+    )
+    y_pred = regr.fit(X, y).predict(X)
+    assert y.shape == y_pred.shape
+    # consistency forward transform
+    if y.ndim == 1:  # create a 2D array and squeeze results
+        y_tran = regr.transformer_.transform(y.reshape(-1, 1))
+    else:
+        y_tran = regr.transformer_.transform(y)
+    _check_standard_scaled(y, y_tran.squeeze())
+    assert y.shape == y_pred.shape
+    # consistency inverse transform
+    assert_allclose(y, regr.transformer_.inverse_transform(y_tran).squeeze())
+    # consistency of the regressor
+    lr = LinearRegression()
+    transformer2 = clone(transformer)
+    if y.ndim == 1:  # create a 2D array and squeeze results
+        lr.fit(X, transformer2.fit_transform(y.reshape(-1, 1)).squeeze())
+        y_lr_pred = lr.predict(X).reshape(-1, 1)
+        y_pred2 = transformer2.inverse_transform(y_lr_pred).squeeze()
+    else:
+        lr.fit(X, transformer2.fit_transform(y))
+        y_lr_pred = lr.predict(X)
+        y_pred2 = transformer2.inverse_transform(y_lr_pred)
+
+    assert_allclose(y_pred, y_pred2)
+    assert_allclose(regr.regressor_.coef_, lr.coef_)
+
+
+def test_transform_target_regressor_2d_transformer_multioutput():
+    # Check consistency with transformer accepting only 2D array and a 2D y
+    # array.
+    X = friedman[0]
+    y = np.vstack((friedman[1], friedman[1] ** 2 + 1)).T
+    transformer = StandardScaler()
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(), transformer=transformer
+    )
+    y_pred = regr.fit(X, y).predict(X)
+    assert y.shape == y_pred.shape
+    # consistency forward transform
+    y_tran = regr.transformer_.transform(y)
+    _check_standard_scaled(y, y_tran)
+    assert y.shape == y_pred.shape
+    # consistency inverse transform
+    assert_allclose(y, regr.transformer_.inverse_transform(y_tran).squeeze())
+    # consistency of the regressor
+    lr = LinearRegression()
+    transformer2 = clone(transformer)
+    lr.fit(X, transformer2.fit_transform(y))
+    y_lr_pred = lr.predict(X)
+    assert_allclose(y_pred, transformer2.inverse_transform(y_lr_pred))
+    assert_allclose(regr.regressor_.coef_, lr.coef_)
+
+
+def test_transform_target_regressor_3d_target():
+    # Non-regression test for:
+    # https://github.com/scikit-learn/scikit-learn/issues/18866
+    # Check with a 3D target with a transformer that reshapes the target
+    X = friedman[0]
+    y = np.tile(friedman[1].reshape(-1, 1, 1), [1, 3, 2])
+
+    def flatten_data(data):
+        return data.reshape(data.shape[0], -1)
+
+    def unflatten_data(data):
+        return data.reshape(data.shape[0], -1, 2)
+
+    transformer = FunctionTransformer(func=flatten_data, inverse_func=unflatten_data)
+    regr = TransformedTargetRegressor(
+        regressor=LinearRegression(), transformer=transformer
+    )
+    y_pred = regr.fit(X, y).predict(X)
+    assert y.shape == y_pred.shape
+
+
+def test_transform_target_regressor_multi_to_single():
+    X = friedman[0]
+    y = np.transpose([friedman[1], (friedman[1] ** 2 + 1)])
+
+    def func(y):
+        out = np.sqrt(y[:, 0] ** 2 + y[:, 1] ** 2)
+        return out[:, np.newaxis]
+
+    def inverse_func(y):
+        return y
+
+    tt = TransformedTargetRegressor(
+        func=func, inverse_func=inverse_func, check_inverse=False
+    )
+    tt.fit(X, y)
+    y_pred_2d_func = tt.predict(X)
+    assert y_pred_2d_func.shape == (100, 1)
+
+    # force that the function only return a 1D array
+    def func(y):
+        return np.sqrt(y[:, 0] ** 2 + y[:, 1] ** 2)
+
+    tt = TransformedTargetRegressor(
+        func=func, inverse_func=inverse_func, check_inverse=False
+    )
+    tt.fit(X, y)
+    y_pred_1d_func = tt.predict(X)
+    assert y_pred_1d_func.shape == (100, 1)
+
+    assert_allclose(y_pred_1d_func, y_pred_2d_func)
+
+
+class DummyCheckerArrayTransformer(TransformerMixin, BaseEstimator):
+    def fit(self, X, y=None):
+        assert isinstance(X, np.ndarray)
+        return self
+
+    def transform(self, X):
+        assert isinstance(X, np.ndarray)
+        return X
+
+    def inverse_transform(self, X):
+        assert isinstance(X, np.ndarray)
+        return X
+
+
+class DummyCheckerListRegressor(DummyRegressor):
+    def fit(self, X, y, sample_weight=None):
+        assert isinstance(X, list)
+        return super().fit(X, y, sample_weight)
+
+    def predict(self, X):
+        assert isinstance(X, list)
+        return super().predict(X)
+
+
+def test_transform_target_regressor_ensure_y_array():
+    # check that the target ``y`` passed to the transformer will always be a
+    # numpy array. Similarly, if ``X`` is passed as a list, we check that the
+    # predictor receive as it is.
+    X, y = friedman
+    tt = TransformedTargetRegressor(
+        transformer=DummyCheckerArrayTransformer(),
+        regressor=DummyCheckerListRegressor(),
+        check_inverse=False,
+    )
+    tt.fit(X.tolist(), y.tolist())
+    tt.predict(X.tolist())
+    with pytest.raises(AssertionError):
+        tt.fit(X, y.tolist())
+    with pytest.raises(AssertionError):
+        tt.predict(X)
+
+
+class DummyTransformer(TransformerMixin, BaseEstimator):
+    """Dummy transformer which count how many time fit was called."""
+
+    def __init__(self, fit_counter=0):
+        self.fit_counter = fit_counter
+
+    def fit(self, X, y=None):
+        self.fit_counter += 1
+        return self
+
+    def transform(self, X):
+        return X
+
+    def inverse_transform(self, X):
+        return X
+
+
+@pytest.mark.parametrize("check_inverse", [False, True])
+def test_transform_target_regressor_count_fit(check_inverse):
+    # regression test for gh-issue #11618
+    # check that we only call a single time fit for the transformer
+    X, y = friedman
+    ttr = TransformedTargetRegressor(
+        transformer=DummyTransformer(), check_inverse=check_inverse
+    )
+    ttr.fit(X, y)
+    assert ttr.transformer_.fit_counter == 1
+
+
+class DummyRegressorWithExtraFitParams(DummyRegressor):
+    def fit(self, X, y, sample_weight=None, check_input=True):
+        # on the test below we force this to false, we make sure this is
+        # actually passed to the regressor
+        assert not check_input
+        return super().fit(X, y, sample_weight)
+
+
+def test_transform_target_regressor_pass_fit_parameters():
+    X, y = friedman
+    regr = TransformedTargetRegressor(
+        regressor=DummyRegressorWithExtraFitParams(), transformer=DummyTransformer()
+    )
+
+    regr.fit(X, y, check_input=False)
+    assert regr.transformer_.fit_counter == 1
+
+
+def test_transform_target_regressor_route_pipeline():
+    X, y = friedman
+
+    regr = TransformedTargetRegressor(
+        regressor=DummyRegressorWithExtraFitParams(), transformer=DummyTransformer()
+    )
+    estimators = [("normalize", StandardScaler()), ("est", regr)]
+
+    pip = Pipeline(estimators)
+    pip.fit(X, y, **{"est__check_input": False})
+
+    assert regr.transformer_.fit_counter == 1
+
+
+class DummyRegressorWithExtraPredictParams(DummyRegressor):
+    def predict(self, X, check_input=True):
+        # In the test below we make sure that the check input parameter is
+        # passed as false
+        self.predict_called = True
+        assert not check_input
+        return super().predict(X)
+
+
+def test_transform_target_regressor_pass_extra_predict_parameters():
+    # Checks that predict kwargs are passed to regressor.
+    X, y = friedman
+    regr = TransformedTargetRegressor(
+        regressor=DummyRegressorWithExtraPredictParams(), transformer=DummyTransformer()
+    )
+
+    regr.fit(X, y)
+    regr.predict(X, check_input=False)
+    assert regr.regressor_.predict_called