# File test/unit/ui/util/observable.rb, line 52
     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