Parameters
        -------
        label_append : str

        Returns
        -------
        pd.DataFrame indexed on metadata, with columns giving frequencies for each category

def get_metadata_freq_df(self, label_append=' freq'):
        '''
        Parameters
        -------
        label_append : str

        Returns
        -------
        pd.DataFrame indexed on metadata, with columns giving frequencies for each category
        '''
        row = self._row_category_ids_for_meta()
        newX = csr_matrix((self._mX.data, (row, self._mX.indices)))
        return self._metadata_freq_df_from_matrix(newX, label_append)