class Faraday::RackBuilder

def use(klass, *args, &block)
  if klass.is_a? Symbol
    use_symbol(Faraday::Middleware, klass, *args, &block)
  else
    raise_if_locked
    warn_middleware_after_adapter if adapter_set?
    @handlers << self.class::Handler.new(klass, *args, &block)
  end
end