generic<T> int dom_fetch(
const &char method,
const &char url,
const ?&char headers,
const ?&char body,
fn void(?&T, &DomFetchResponse) handler,
?&T userdata,
)generic<T> int dom_fetch(
const &char method,
const &char url,
const ?&char headers,
const ?&char body,
fn void(?&T, &DomFetchResponse) handler,
?&T userdata,
)