pub fn center(
  inner: #(Int, Int),
  outer: #(Int, Int),
) -> #(#(Int, Int), #(Int, Int))

pub fn do_fetch(
  request: Request(BitArray),
) -> Promise(Result(Response(BitArray), FetchError))

pub fn do_wait(delay: Int) -> Promise(Nil)

pub fn open(
  url: String,
  frame_size: #(Int, Int),
) -> Result(Window, String)

pub fn receive_redirect(
  popup: Window,
  wait: Int,
) -> Promise(String)

pub fn run(task: Effect(a)) -> Promise(Result(a, Snag))