bar.rb

class Bar 
  include MongoMapper::Document
  normalize_attributes :name
  key :name, String

end

console

Loading development environment (Rails 2.3.5)
rails development: main 
>> Bar
NoMethodError: undefined method `normalize_attributes' for Bar:Class
	from /Users/202362/Code/foo/vendor/gems/mongo_mapper-0.6.6/lib/mongo_mapper/document.rb:328:in `method_missing'
	from /Users/202362/Code/foo/app/models/bar.rb:4
	from /Users/202362/Code/foo/vendor/rails/activesupport/lib/active_support/dependencies.rb:380:in `load_without_new_constant_marking'
	from /Users/202362/Code/foo/vendor/rails/activesupport/lib/active_support/dependencies.rb:380:in `load_file'
	from /Users/202362/Code/foo/vendor/rails/activesupport/lib/active_support/dependencies.rb:521:in `new_constants_in'
	from /Users/202362/Code/foo/vendor/rails/activesupport/lib/active_support/dependencies.rb:379:in `load_file'
	from /Users/202362/Code/foo/vendor/rails/activesupport/lib/active_support/dependencies.rb:259:in `require_or_load'
	from /Users/202362/Code/foo/vendor/rails/activesupport/lib/active_support/dependencies.rb:425:in `load_missing_constant'
	from /Users/202362/Code/foo/vendor/rails/activesupport/lib/active_support/dependencies.rb:80:in `const_missing'
	from /Users/202362/Code/foo/vendor/rails/activesupport/lib/active_support/dependencies.rb:92:in `const_missing'
	from (irb):1

init.rb

require File.join(File.dirname(__FILE__), *%w[.. lib attribute_normalizer])
module MongoMapper
  module Document
    module ClassMethods
      include AttributeNormalizer
      def normalize_attributes(*args)
        puts "Now I am over heah!"
      end
    end
  end
end