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: singleton.rb
    path of file: ./repos/opal/stdlib
    
    the code of the file until where you have to start completion: module Singleton
  def clone
    raise TypeError, "can't clone instance of singleton #{self.class}"
  end

  def dup
    raise TypeError, "can't dup instance of singleton #{self.class}"
  e
    
    def __init__(klass)
      klass.instance_eval do
        @singleton__instance__ = nil
      end
      def klass.instance
        return @singleton__instance__ if @singleton__instance__
        @singleton__instance__ = new
      end
      klass
    end