'Add signature to the chord the current task is a member of.
.. versionadded:: 4.0
Currently only supported by the Redis result backend.
Arguments:
sig (~@Signature): Signature to extend chord with.
lazy (bool): If enabled the new task won\'t actually be called,
and ``sig.delay()`` must be called manually.'

def add_to_chord(self, sig, lazy=False):

    if (not self.request.chord):
        raise ValueError(u'Current    task    is    not    member    of    any    chord')
    result = sig.freeze(group_id=self.request.group, chord=self.request.chord, root_id=self.request.root_id)
    self.backend.add_to_chord(self.request.group, result)
    return (sig.delay() if (not lazy) else sig)
