A 'mapReduce' function changed 'function' to instance '\<Object\>' of 'Code' class.

After mapReduce function executed with 'scope: {util: XXX}', the 'compare' function of XXX has been changed to an instance '\<Object\>' of 'Code' class.

<Example>

```javascript
var XXX = {
  compare: function (a, b) {
    return a == b ? 0 : a < b ? -1 : 1
  }
}
```

```javascript
XXX.compare(1, 2); // -1
```

```javascript
collection.mapReduce(
  map,
  reduce,
  {
    scope: {util: XXX}
  }
);
```

```javascript
XXX.compare(1, 2); // TypeError: Property 'compare' of object #<Object> is not a function
```