def object_id_from_datetime(from_datetime=None,span_days=0,span_hours=0,span_minutes=0,span_seconds=0,span_weeks=0):
    '''根据时间手动生成一个objectid，此id不作为存储使用'''
    if not from_datetime:
        from_datetime = datetime.datetime.now()
    from_datetime = from_datetime + datetime.timedelta(days=span_days,hours=span_hours,minutes=span_minutes,weeks=span_weeks)
    return ObjectId.from_datetime(generation_time=from_datetime)
#//python/9050