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: manager.rb
    path of file: ./repos/souls/lib/souls/cli/generate
    
    the code of the file until where you have to start completion: module SOULs
  class Generate < Thor
    desc "manager [MANAGER_NAME]", "Generate GraphQL Mutation Template"
    method_option :mutation, aliases: "--mutation", required: true, desc: "Mutation File 
    
    def create_manager(class_name, mutation)
      singularized_class_name = class_name.underscore.singularize
      file_dir = "./app/graphql/mutations/managers/#{singularized_class_name}_manager"
      FileUtils.mkdir_p(file_dir) unless Dir.exist?(file_dir)
      file_path = "#{file_dir}/#{mutation}.rb"
      raise(StandardError, "Already Exist!") if File.exist?(file_path)

      File.open(file_path, "w") do |f|
        f.write(<<~TEXT)
          module Mutations
            module Managers::#{singularized_class_name.camelize}Manager
              class #{mutation.underscore.camelize} < BaseMutation
                description "#{mutation} description"
                ## Edit `argument` and `field`
                argument :argument, String, required: false

                field :response, String, null: false

                def resolve(args)
                  # Define Here
                  puts(args)
                  { response: "success!" }
                end
              end
            end