Return the filepath of the parent function.
// File file:///home/hello/parent.ts
import { child } from './child.ts';
function parent() {
child();
}
// File file:///home/hello/child.ts
import caller from 'https://raw.githubusercontent.com/apiel/caller/master/caller.ts';
export function child() {
console.log(caller());
// should return file:///home/hello/parent.ts
}