handler will no longer be called if args match argspec

        :param argspec: instance of ArgSpec - args to be matched

def unbind(self, handler, argspec):
        """
        handler will no longer be called if args match argspec

        :param argspec: instance of ArgSpec - args to be matched
        """
        self.handlers[argspec.key].remove((handler, argspec))
        if not len(self.handlers[argspec.key]):
            del self.handlers[argspec.key]