code: def _set_value(self, value):
          
          assert not self.ready()
          self._data = value
          self._success = True
          self._event.set()
          if self._collector is not None:
              self._collector.notify_ready(self)
          if self._callback is not None:
              try:
                  self._callback(value)
              except:
                  traceback.print_exc()
docs: Called by a Job object to tell the result is ready, and
          provides the value of this result. The object will become
          ready and successful. The collector's notify_ready() method
          will be called, and the callback method too