Typescript wrapper for node util promisify

promise.ts

import * as util from "util";

type Maybe<T> = T | undefined | null;

export function promisify<Args, R>(
  fn: (arg: Args, callback: (e: Maybe<Error>, result: R) => void) => void,
  self?: any
): (arg: Args) => Promise<R> {
  return util.promisify(fn).bind(self);
}