langchain/utils.py/MockDateTime/now
class MockDateTime:        def now(cls):  # type: ignore
            # Create a copy of dt_value.
            return datetime.datetime(
                dt_value.year,
                dt_value.month,
                dt_value.day,
                dt_value.hour,
                dt_value.minute,
                dt_value.second,
                dt_value.microsecond,
                dt_value.tzinfo,
            )