'Associate listener with message types created by this Dispatcher.
@param listener callable to receive messages
@param *types zero or more message types to associate with listener
@return True if associated with one or more handler; otherwise False'

def register(self, listener, *types):

    count = 0
    for messagetype in types:
        key = maybeName(messagetype)
        listeners = self.listeners.setdefault(key, [])
        if (listener not in listeners):
            listeners.append(listener)
            count += 1
    return (count > 0)
