chord returning the header's task group

progresschord.py

class ProgressChord(chord):
 
    """
    Chord that returns both the callback's AsyncResult and the group's
    AsyncResult.
    """
 
    # See:
    # http://stackoverflow.com/questions/15441101/how-to-track-the-progress-of-individual-tasks-inside-a-group-which-forms-the-hea
    # https://groups.google.com/forum/?fromgroups=#!topic/celery-users/xSdxI-Z08Cw
 
    def __call__(self, body=None, **kwargs):
        # Taken from celery source code, celery.canvas
        _chord = self.Chord
        body = (body or self.kwargs['body']).clone()
        kwargs = dict(self.kwargs, body=body, **kwargs)
        if _chord.app.conf.CELERY_ALWAYS_EAGER:
            return self.apply((), kwargs)
        callback_id = body.options.setdefault('task_id', uuid())
        r = _chord(**kwargs)
        return _chord.AsyncResult(callback_id), r