text: class Submittable(object):
      """
      Object directly submittable to an executor, without wrapping:
      E.g. an ActivityTask but not an Activity.
      """
  
      def propagate_attribute(self, attr, val):
          pass
  
  
  class SubmittableContainer(object):
      """
      Objects where submission returns either Submittable or SubmittableContainer objects
  
      We cannot pass those objects directly to the executor
      """
  
      def propagate_attribute(self, attr, val):
          pass
  