Lua set proxy is not working at all

[syaiful6]

I trying to use proxy with splash, so according to documentation I can do this with "on_request" callback and request.set_proxy, but when I go to https://httpbin.org/ip I still see my IP, not the proxy IP.

The lua source is:

function main(splash, args)
  splash:on_request(function(request)
    request.set_proxy{"proxy.crawlera.com", 8011, username = "xxxxxxxxxx", password = "", type = "HTTP"}
  end)
  assert(splash:go(args.url))
  assert(splash:wait(5.0))
  return {
    png = splash:png(),
    har = splash:har(),
  }
end

I got this error in the splash container:

I am not sure why it complaints set_proxy require 2 positional arguments, since I already give it all required arguments. Am I missing something?

Splash version: 3.5