code: def _copy_future_state(source, dest):
      
      assert source.done()
      if dest.cancelled():
          return
      assert not dest.done()
      if source.cancelled():
          dest.cancel()
      else:
          exception = source.exception()
          if exception is not None:
              dest.set_exception(exception)
          else:
              result = source.result()
              dest.set_result(result)
docs: Internal helper to copy state from another Future.
      The other Future may be a concurrent.futures.Future.