code: function(opSet, target) {
        var self = this;
        Parse._objectEach(opSet, function(change, key) {
          target[key] = change._estimate(target[key], self, key);
          if (target[key] === Parse.Op._UNSET) {
            delete target[key];
          }
        });
      }
docs: Applies the set of Parse.Op in opSet to the object target.