langchain/memory/chat_message_histories/sql.py/SQLChatMessageHistory/_create_table_if_not_exists
class SQLChatMessageHistory:    def _create_table_if_not_exists(self) -> None:
        DynamicBase = declarative_base()
        self.Message = create_message_model(self.table_name, DynamicBase)
        # Create all does the check for us in case the table exists.
        DynamicBase.metadata.create_all(self.engine)