# File lib/monkey/ext.rb, line 70
      def feature(name, mode = :instance, &block)
        case mode
        when :instance then block.call
        when :class then class_methods(&block)
        when :shared
          feature(name, :instance, &block)
          feature(name, :class, &block)
        else raise ArgumentError, "unkown mode #{mode.inspect}"
        end
      end