class Pipe():

    def build_pipeline(self):
        Stage1 = Object_X()
        Stage2 = Object_Y()
        self.pipeline = [Stage1, Stage2]

    def run():
        for p in pipeline:
            # execute p's respective run()
            # pass this to the next element in pipeline

class Object_X():
   # all kinds of definition

   def run()
       # do something

class Object_Y():
   # all kinds of definition

   def run()
       # do something