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: builder.rb
    path of file: ./repos/karafka/lib/karafka/routing
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module Karafka
  module Routing
    # Builder used as a DSL layer for building consumers and telling th
    
      def consumer_group(group_id, &block)
        consumer_group = find { |cg| cg.name == group_id.to_s }

        if consumer_group
          Proxy.new(consumer_group, &block).target
        else
          consumer_group = ConsumerGroup.new(group_id.to_s)
          self << Proxy.new(consumer_group, &block).target
        end