def to_api_data(self, restrict_keys=None):
        """ Returns a dict to communicate with the server

        :param restrict_keys: a set of keys to restrict the returned data to
        :rtype: dict
        """
        cc = self._cc  # alias
        data = {
            cc('column_hidden'): self._column_hidden,
            cc('row_hidden'): self._row_hidden,
            cc('formulas'): self._formulas,
            cc('formulas_local'): self._formulas_local,
            cc('formulas_r1_c1'): self._formulas_r1_c1,
            cc('number_format'): self._number_format,
            cc('values'): self._values,
        }

        if restrict_keys:
            for key in list(data.keys()):
                if key not in restrict_keys:
                    del data[key]
        return data
Returns a dict to communicate with the server

        :param restrict_keys: a set of keys to restrict the returned data to
        :rtype: dict