Repository: scikit-learn/scikit-learn
File: sklearn/tree/_classes.py (Python)

Code before:
            StrOptions({"squared_error", "absolute_error", "poisson"}),
            Hidden(Criterion),
        ],
    }

    def __init__(
        self,
        *,
        criterion="squared_error",
        splitter="best",
        max_depth=None,
        min_samples_split=2,
        min_samples_leaf=1,
        min_weight_fraction_leaf=0.0,
        max_features=None,
        random_state=None,
        max_leaf_nodes=None,
        min_impurity_decrease=0.0,
        ccp_alpha=0.0,
        monotonic_cst=None,
    ):
        if isinstance(criterion, str) and criterion == "friedman_mse":
            criterion = "squared_error"
            warnings.warn(
                'Value `"friedman_mse"` for `criterion` is deprecated and will be '
                'removed in 1.10. It maps to `"squared_error"` as both '
                'were always equivalent. Use `criterion="squared_error"` '
                "to remove this warning.",
                FutureWarning,
            )
        super().__init__(
            criterion=criterion,
            splitter=splitter,
            max_depth=max_depth,
            min_samples_split=min_samples_split,
            min_samples_leaf=min_samples_leaf,
            min_weight_fraction_leaf=min_weight_fraction_leaf,
            max_features=max_features,
            max_leaf_nodes=max_leaf_nodes,
            random_state=random_state,
            min_impurity_decrease=min_impurity_decrease,
            ccp_alpha=ccp_alpha,
            monotonic_cst=monotonic_cst,
        )

    @_fit_context(prefer_skip_nested_validation=True)
    def fit(self, X, y, sample_weight=None, check_input=True):
        """Build a decision tree regressor from the training set (X, y).

        Parameters
        ----------

Review comment (suggestion):
```suggestion
                'removed in 1.11. It maps to `"squared_error"` as both '
```

Code after:
            StrOptions({"squared_error", "absolute_error", "poisson"}),
            Hidden(Criterion),
        ],
    }

    def __init__(
        self,
        *,
        criterion="squared_error",
        splitter="best",
        max_depth=None,
        min_samples_split=2,
        min_samples_leaf=1,
        min_weight_fraction_leaf=0.0,
        max_features=None,
        random_state=None,
        max_leaf_nodes=None,
        min_impurity_decrease=0.0,
        ccp_alpha=0.0,
        monotonic_cst=None,
    ):
        if isinstance(criterion, str) and criterion == "friedman_mse":
            # TODO(1.11): remove support of "friedman_mse" criterion.
            criterion = "squared_error"
            warnings.warn(
                'Value `"friedman_mse"` for `criterion` is deprecated and will be '
                'removed in 1.11. It maps to `"squared_error"` as both '
                'were always equivalent. Use `criterion="squared_error"` '
                "to remove this warning.",
                FutureWarning,
            )
        super().__init__(
            criterion=criterion,
            splitter=splitter,
            max_depth=max_depth,
            min_samples_split=min_samples_split,
            min_samples_leaf=min_samples_leaf,
            min_weight_fraction_leaf=min_weight_fraction_leaf,
            max_features=max_features,
            max_leaf_nodes=max_leaf_nodes,
            random_state=random_state,
            min_impurity_decrease=min_impurity_decrease,
            ccp_alpha=ccp_alpha,
            monotonic_cst=monotonic_cst,
        )

    @_fit_context(prefer_skip_nested_validation=True)
    def fit(self, X, y, sample_weight=None, check_input=True):
        """Build a decision tree regressor from the training set (X, y).

        Parameters