Note: this function involves making copies of the index in memory.

        Args:
            axis: Axis to extract indices.
            indices: Indices to convert to numerical.

        Returns:
            An Index object.

def global_idx_to_numeric_idx(self, axis, indices):
        """
        Note: this function involves making copies of the index in memory.

        Args:
            axis: Axis to extract indices.
            indices: Indices to convert to numerical.

        Returns:
            An Index object.
        """
        assert axis in ["row", "col", "columns"]
        if axis == "row":
            return pandas.Index(
                pandas.Series(np.arange(len(self.index)), index=self.index)
                .loc[indices]
                .values
            )
        elif axis in ["col", "columns"]:
            return pandas.Index(
                pandas.Series(np.arange(len(self.columns)), index=self.columns)
                .loc[indices]
                .values
            )