langchain/utilities/spark_sql.py/SparkSQL/get_usable_table_names
class SparkSQL:    def get_usable_table_names(self) -> Iterable[str]:
        """Get names of tables available."""
        if self._include_tables:
            return self._include_tables
        # sorting the result can help LLM understanding it.
        return sorted(self._all_tables - self._ignore_tables)