'Callback that performs a blocking actor call to the real callback.
This is passed to audio, which is allowed to call this code from the
audio thread. We pass execution into the core actor to ensure that
there is no unsafe access of state in core. This must block until
we get a response.'

def _on_about_to_finish_callback(self):

    self.core.actor_ref.ask({u'command': u'pykka_call', u'args': tuple(), u'kwargs': {}, u'attr_path': (u'playback', u'_on_about_to_finish')})
