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: removed_cop.rb
    path of file: ./repos/rubocop/lib/rubocop/config_obsoletion
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module RuboCop
  class ConfigObsoletion
    # Encapsulation of a ConfigObsoletion rule for removing
    # a previously defined cop.
    #
    
      def rule_message
        base = format(BASE_MESSAGE, old_name: old_name)

        if reason
          "#{base} since #{reason.chomp}."
        elsif alternatives
          "#{base}. Please use #{to_sentence(alternatives, connector: 'and/or')} instead."
        else
          "#{base}."
        end