custom

# File actionpack/lib/action_controller/metal/mime_responds.rb, line 486
      def custom(mime_type, &block)
        mime_type = Mime::Type.lookup(mime_type.to_s) unless mime_type.is_a?(Mime::Type)
        @responses[mime_type] ||= if block_given?
          block
        else
          VariantCollector.new(@variant)
        end
      end