You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: observable.rb
    path of file: ./repos/ruby-packer/ruby/gems/test-unit-3.3.4/lib/test/unit/util
    
    the code of the file until where you have to start completion: #--
#
# Author:: Nathaniel Talbott.
# Copyright:: Copyright (c) 2000-2002 Nathaniel Talbott. All rights reserved.
# License:: Ruby lic
    
        def notify_listeners(channel_name, *arguments)
          channel = channels[channel_name]
          return 0 unless (channel)
          listeners = channel.values
          listeners.each { |listener| listener.call(*arguments) }
          return listeners.size
        end