code: function(Ctor) {
  	return function() {
  		var args = Array.from(arguments);
  		return new Promise(function(resolve, reject) {
  			var req = Object.create(Ctor.prototype);
  			Ctor.apply(req, args);
  			req.once('src', function(err, src) {
  				if (err) {
  					reject(err);
  				} else {
  					resolve(src);
  				}
  			});
  		});
  	};
  }
docs: Helper to return a promise returning function for the result of an (Ctor-type) ApiRequest.