code: def iter(self, prev=None):
          
  
          if self.next:
              generator = self.next.iter(self.func(prev, *self.args, **self.kw))
          else:
              generator = self.func(prev, *self.args, **self.kw)
          return generator
docs: Return an generator as iterator object.
  
          :param prev: Previous Pipe object which used for data input.
          :returns: A generator for iteration.