code: function (id, callback) {
      this.loadViewModel(id, function (err, vm) {
        if (err) {
          return callback(err);
        }
  
        if (!vm || vm.actionOnCommit === 'create') {
          return callback(null, null);
        }
  
        callback(null, vm);
      });
    }
docs: Loads a viewModel object by id if exists.
  @param {String}   id       The viewModel id.
  @param {Function} callback The function, that will be called when the this action is completed.
  `function(err, vm){}` vm is of type Object or null