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

require 'singleton'
require 'active_decorator/helpers'
require 'active_decorator/decorated'

module ActiveDecorator
  class Decorator
    include Singleton

    def initialize
      @decorators = {}
    end

    # Decorates th
    
    def decorate(obj)
      return obj if defined?(Jbuilder) && (Jbuilder === obj)

      case obj
      when Array
        obj.each {|e| decorate e }
      when Hash
        obj.each_value {|v| decorate v }
      when nil, true, false
        # Do nothing
      else
        if defined? ActiveRecord
          if obj.is_a? ActiveRecord::Relation
            return decorate_relation obj
          elsif ActiveRecord::Base === obj
            obj.extend ActiveDecorator::Decorated unless ActiveDecorator::Decorated === obj
          end