code: function unpromisify(fn) {
    return function () {
      for (var _len = arguments.length, args = Array(_len), _key = 0; _key < _len; _key++) {
        args[_key] = arguments[_key];
      }
  
      var callback = function callback() {};
  
      /* If last argument is a callback, separate it out */
      if (typeof _lodash2['default'].last(args) === 'function') {
        callback = _lodash2['default'].last(args);
        args = _lodash2['default'].take(args, args.length - 1);
      }
  
      /* Call the function and wrap the promise */
      return _bluebird2['default']['try'](function () {
        return fn.apply(undefined, _toConsumableArray(args));
      }).nodeify(callback);
    };
  }
docs: unpromisify(1)
  
  @description                Wraps a promise-returning function into a
  universal function that returns a promise AND
  accepts a node-style callback.
  @param          {fn}        promise-returning function to wrap.
  @returns        {Function}  Node-style callback-accepting function.