def get_mapping_meta(self):
        """return the current _meta field."""
        m = self.get_mapping()
        doc_type = self._doc_type
        if doc_type is None:
            # fetch doc_type from mapping
            assert len(m) == 1, "More than one doc_type found, not supported when self._doc_type " + \
                                "is not initialized"
            doc_type = list(m.keys())[0]
        return {"_meta": m[doc_type]["_meta"]}