after patch individual json field, ref string mapped object

After patch a json field, ex) ` post.$query().patch({ 'jsonFields:subnode': 1 })`

`jsonFields:subnode` is mapped as a object property.

like,
```
Post {
  jsonFields: {
    subnode: 1
  },
  'jsonFields:subnode`: 1
}
```

is it bug? or expected?