Transform X using one-hot encoding.

        Parameters
        ----------
        X : array-like or sparse matrix, shape=(n_samples, n_features)
            Dense array or sparse matrix.

        Returns
        -------
        X_out : sparse matrix if sparse=True else a 2-d array, dtype=int
            Transformed input.

def transform(self, X):
        """Transform X using one-hot encoding.

        Parameters
        ----------
        X : array-like or sparse matrix, shape=(n_samples, n_features)
            Dense array or sparse matrix.

        Returns
        -------
        X_out : sparse matrix if sparse=True else a 2-d array, dtype=int
            Transformed input.
        """
        return _transform_selected(
            X, self._transform,
            self.categorical_features,
            copy=True
        )