docs: def clear(
              self  # type: ORMTask
      ):
          """Delete all objects created by this task.
  
          Iterate over `self.object_classes` and delete all objects of the listed classes.
          """
          # mark this task as incomplete
          self.mark_incomplete()
  
          # delete objects
          for object_class in self.object_classes:
              self.session.query(object_class).delete()
  
          self.close_session()