code: def deserialize_unix(attr):
          
          if isinstance(attr, ET.Element):
              attr = int(attr.text)
          try:
              date_obj = datetime.datetime.fromtimestamp(attr, TZ_UTC)
          except ValueError as err:
              msg = "Cannot deserialize to unix datetime object."
              raise_with_traceback(DeserializationError, msg, err)
          else:
              return date_obj
docs: Serialize Datetime object into IntTime format.
          This is represented as seconds.
  
          :param int attr: Object to be serialized.
          :rtype: Datetime
          :raises: DeserializationError if format invalid