langchain/memory/chat_message_histories/postgres.py/PostgresChatMessageHistory/_create_table_if_not_exists
class PostgresChatMessageHistory:    def _create_table_if_not_exists(self) -> None:
        create_table_query = f"""CREATE TABLE IF NOT EXISTS {self.table_name} (
            id SERIAL PRIMARY KEY,
            session_id TEXT NOT NULL,
            message JSONB NOT NULL
        );"""
        self.cursor.execute(create_table_query)
        self.connection.commit()