operator $in not working?

```
var db, jsonqueryEngine, levelQuery, levelup, pairs;

levelQuery = require('level-queryengine');

jsonqueryEngine = require('jsonquery-engine');

pairs = require('pairs');

levelup = require('levelup');

db = levelQuery(levelup("./db", {
valueEncoding: 'json'
}));

db.query.use(jsonqueryEngine());

db.ensureIndex('Id');

```

then if i execute:

```
dbl.query( { Id: 1 } ).on( "data", function(data){ console.log( "got data", data); } ).on( "end", function(){console.log( "end" )});
```

i get one result on "data"

but if i execute:

```
dbl.query( { Id: { $in: [1] } } ).on( "data", function(data){ console.log( "got data", data); } ).on( "end", function(){console.log( "end" )});
```

only the "end" event is being triggered.

any ideas?