code: def parse_stream(cls, iterable):
          
          parser = Parser()
          for message_dict in iterable:
              completed, parser = parser.add(message_dict)
              for task in completed:
                  yield task
          for task in parser.incomplete_tasks():
              yield task
docs: Parse a stream of messages into a stream of L{Task} instances.
  
          :param iterable: An iterable of serialized Eliot message dictionaries.
  
          :return: An iterable of parsed L{Task} instances. Remaining
              incomplete L{Task} will be returned when the input stream is
              exhausted.