Unregisters an existing signal

        :param signal: Name of the signal

def unregister(self, signal):
        """
        Unregisters an existing signal

        :param signal: Name of the signal
        """
        if signal in self.signals.keys():
            del(self.signals[signal])
            self.__log.debug("Signal %s unregisterd" % signal)
        else:
            self.__log.debug("Signal %s does not exist and could not be unregistered.")