docs: def iterator(self, envelope):
  		""" :meth:`WMessengerOnionSessionFlowProto.iterator` implementation
  		"""
  		for pair in self.__pairs:
  			if pair.comparator().match(envelope) is True:
  				return pair.flow().iterator(envelope)
  
  		if self.__default_flow is not None:
  			return self.__default_flow.iterator(envelope)