code: def set_result(self, result):
          
          for future in self.traverse():
              # All cancelled futures should have callbacks to removed itself
              # from this linked list. However, these callbacks are scheduled in
              # an event loop, so we could still find them in our list.
              future.set_result(result)
          if not self.done():
              super().set_result(result)
docs: Complete all tasks.