def must_implement(*args)
      parsed_args(args).each do |method, arity|
        raise_interface_error(method, arity) unless valid_method?(method, arity)
      end
    end
def must_implement(*args)
      parsed_args(args).each do |method, arity|
        raise_interface_error(method, arity) unless valid_method?(method, arity)
      end
    end
Errors raised here identify the class_name that is not implementing or is
 implemented with the wrong arity required by the Interface.