'Save changes to the model instance.
If _signal=False is in `kw` the on_change() callbacks won\'t be called.'

def save(self, *args, **kw):

    signal = kw.pop('_signal', True)
    result = super(OnChangeMixin, self).save(*args, **kw)
    if (signal and (self.__class__ in _on_change_callbacks)):
        self._send_changes(self._initial_attr, dict(self.__dict__))
    self.reset_attrs()
    return result
