'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'

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()
