code: def _set_class_path(cls, module_dict=sys.modules):
      
      # Do not traverse the class hierarchy fetching the class path attribute.
      found = cls.__dict__.get('_class_path')
      if found is not None:
        return
  
      # Do not set the _class_path for the base-class, otherwise all children's
      # lookups for _class_path will fall through and return 'Pipeline' above.
      # This situation can happen if users call the generic Pipeline.from_id
      # to get the result of a Pipeline without knowing its specific class.
      if cls is Pipeline:
        return
  
      class_path = '%s.%s' % (cls.__module__, cls.__name__)
      # When a WSGI handler is invoked as an entry point, any Pipeline class
      # defined in the same file as the handler will get __module__ set to
      # __main__. Thus we need to find out its real fully qualified path.
      if cls.__module__ == '__main__':
        for name, module in module_dict.items():
          if name == '__main__':
            continue
          found = getattr(module, cls.__name__, None)
          if found is cls:
            class_path = '%s.%s' % (name, cls.__name__)
            break
      cls._class_path = class_path
docs: Sets the absolute path to this class as a string.
  
      Used by the Pipeline API to reconstruct the Pipeline sub-class object
      at execution time instead of passing around a serialized function.
  
      Args:
        module_dict: Used for testing.