# File test/unit/util/observable.rb, line 51
                                def remove_listener(channel_name, listener_key)
                                        channel = channels[channel_name]
                                        unless (channel.nil?)
                                                key = listener_key
                                                if (listener_key.instance_of?(Proc))
                                                        key = ProcWrapper.new(listener_key)
                                                end
                                                if (channel.has_key?(key))
                                                        return channel.delete(key)
                                                end
                                        end
                                        return nil
                                end