Unbind from dispatchers and target function.

        :return: set of tuples containing [argspec, dispatcher]

def unbind(self):
        """
        Unbind from dispatchers and target function.

        :return: set of tuples containing [argspec, dispatcher]
        """
        args_dispatchers = set()
        f = self._wf()
        if f is not None:
            for ad_list in self.bound_to.values():
                args_dispatchers.update(ad_list)
                for argspec, dispatcher in ad_list:
                    dispatcher.unbind(self.f, argspec)
            del f.__dict__['__mnd__']
        self.bound_to = {}
        return args_dispatchers