'process signal `s`.  All of the functions registered to receive
callbacks on `s` will be called with ``**args`` and ``**kwargs``'

def process(self, s, *args, **kwargs):

    if (s in self.callbacks):
        for (cid, proxy) in list(six.iteritems(self.callbacks[s])):
            try:
                proxy(*args, **kwargs)
            except ReferenceError:
                self._remove_proxy(proxy)
