def METHOD_NAME(self) -> Iterable[str]:
    if self._usable_tables is None:
        original_db = self._engine.session.database
        ret = self._call_engine(['show databases;'])
        dbs = [lst[0] for lst in ret.data if lst[0] != 'information_schema']
        usable_tables = []
        for db in dbs:
            if db != 'mindsdb':
                try:
                    ret = self._call_engine([f'use `{db}`;', 'show tables;'])
                    tables = [lst[0] for lst in ret.data if lst[0] != 'information_schema']
                    if tables:
                        usable_tables.extend([f'{db}.{t}' for t in tables])
                except Exception:
                    pass
                finally:
                    _ = self._call_engine([f'use {original_db};'])
        self._usable_tables = usable_tables
    return self._usable_tables