def _get_index(self, index=None):
if self.is_freq_type:<EOL><INDENT>if index is None:<EOL><INDENT>index = self._on<EOL><DEDENT>return index, index.asi8<EOL><DEDENT>return index, index<EOL>
Return index as ndarrays.

Returns
-------
tuple of (index, index_as_ndarray)