code: def datetime(self):
          
          try:
              dt = self._tick_dict['datetime']
          except (KeyError, ValueError):
              return datetime.datetime.min
          else:
              if not isinstance(dt, datetime.datetime):
                  if dt > 10000000000000000:  # ms
                      return convert_ms_int_to_datetime(dt)
                  else:
                      return convert_int_to_datetime(dt)
              return dt
docs: [datetime.datetime] 当前快照数据的时间戳