def get_column(self, X, column):
        """Return a column of the given matrix.

        Args:
            X: `numpy.ndarray` or `pandas.DataFrame`.
            column: `int` or `str`.

        Returns:
            np.ndarray: Selected column.
        """
        if isinstance(X, pd.DataFrame):
            return X[column].values

        return X[:, column]
Return a column of the given matrix.

        Args:
            X: `numpy.ndarray` or `pandas.DataFrame`.
            column: `int` or `str`.

        Returns:
            np.ndarray: Selected column.