code: function (flags, callback, args, ms) {
          var status = {},
              sealed;
  
          // ensure that the callback times out after a while
          callback = backpack.timeback(callback, ms, null, function () {
              sealed = true;
          });
  
          return function (err, flag, value) {
              if (sealed) { return; } // do  not proceed of it is sealed
              status[flag] = value;
  
              if (err) { // on error we directly call the callback and seal subsequent calls
                  sealed = true;
                  status = null;
                  callback.call(status, err);
  
                  return;
              }
  
              // if any flag is not defined, we exit. when all flags hold a value, we know that the end callback has to be
              // executed.
              for (var i = 0, ii = flags.length; i < ii; i++) {
                  if (!status.hasOwnProperty(flags[i])) { return; }
              }
  
              sealed = true;
              status = null;
              callback.apply(status, args);
          };
      }
docs: Convert a callback into a function that is called multiple times and the callback is actually called when a set
  of flags are set to true
  
  @param {Array} flags
  @param {Function} callback
  @param {Array} args
  @param {Number} ms
  @returns {Function}