2018-fumichan-thesis / form-sample / vendor / bundle / ruby / 2.5.0 / gems / backports-3.11.4 / lib / backports / 1.9.2 / kernel / singleton_class.rb

unless Kernel.method_defined? :singleton_class
  module Kernel
    def singleton_class
      class << self; self; end
    end
  end
end