def _dbs_by_group(self, group, check_len=None):
        dbs = self.partition_config['groups'][group]
        if check_len:
            assert len(dbs) == check_len
        return dbs
Given a database group, returns the list of dbs associated with it
dataset/ETHPy150Open dimagi/commcare-hq/corehq/sql_db/config.py/PartitionConfig._dbs_by_group