def call(env)
      env['x-rack.flash'] ||= Rack::Flash::FlashHash.new(env['rack.session'], @opts)

      if @opts[:sweep]
        env['x-rack.flash'].flag!
      end

      res = @app.call(env)

      if @opts[:sweep]
        env['x-rack.flash'].sweep!
      end

      res
    end
def call(env)
      env['x-rack.flash'] ||= Rack::Flash::FlashHash.new(env['rack.session'], @opts)

      if @opts[:sweep]
        env['x-rack.flash'].flag!
      end

      res = @app.call(env)

      if @opts[:sweep]
        env['x-rack.flash'].sweep!
      end

      res
    end
-------------------------------------------------------------------------
 - Rack Middleware implementation