code: def modified(self):
          
          modified_time = self._properties.get("lastModifiedTime")
          if modified_time is not None:
              # modified_time will be in milliseconds.
              return google.cloud._helpers._datetime_from_microseconds(
                  1000.0 * float(modified_time)
              )
docs: Union[datetime.datetime, None]: Datetime at which the dataset was
          last modified (:data:`None` until set from the server).