Returns a dictionary with the key as the es_index name and the
        object is a list of rdfclasses for that index

        args:
            None

def list_indexes(cls):
        """
        Returns a dictionary with the key as the es_index name and the
        object is a list of rdfclasses for that index

        args:
            None
        """

        cls_list = cls.list_mapped_classes()
        rtn_obj = {}
        for key, value in cls_list.items():
            idx = value.es_defs.get('kds_esIndex')[0]
            try:
                rtn_obj[idx].append(value)
            except KeyError:
                rtn_obj[idx] = [value]
        return rtn_obj