code: def _decode_error(self):
          
          error_qname = self._ns_prefix + "error"
          for child in self._element:
              if child.tag == error_qname:
                  self._error = StanzaErrorElement(child)
                  return
          raise BadRequestProtocolError("Error element missing in"
                                                              " an error stanza")
docs: Decode error element of the stanza.