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: matrix.rb
    path of file: ./repos/gitlabhq/lib/gitlab/ci/config/entry/product
    
    the code of the file until where you have to start completion: # frozen_string_literal: true

module Gitlab
  module Ci
    class Config
      module Entry
        ##
        # Entry that represents matrix style parallel builds.
        #
        module Product
          class Matrix < ::Gitlab::Config::Entry::Node
            include ::Gitlab::Utils::StrongMemoize
            include ::Gitlab::Config::Entry::Validatable
            include ::Gitlab::Config::Entry::Attributable


    
            def compose!(deps = nil)
              super(deps) do
                @config.each_with_index do |variables, index|
                  @entries[index] = ::Gitlab::Config::Entry::Factory.new(Entry::Product::Variables)
                    .value(variables)
                    .with(parent: self, description: 'matrix variables definition.') # rubocop:disable CodeReuse/ActiveRecord
                    .create!
                end

                @entries.each_value do |entry|
                  entry.compose!(deps)
                end
              end
            end