title: Mongoose Upsert, Syntax Error
body: <p>I have experiencing a problem upserting with Mongoose. It says Syntax is invalid, says <code>unexpected token "."</code> at last line. But I cannot understand what is really wrong. I have been looking into it for more than one hour, am I missing a simple concept?</p>
  
  <pre><code>var seriesSchema = new Schema({
      type : {type: Number, default: 1},
      features: {
          tvdb_id: {type: Number, unique: true},
          ....
      },
      created : {type: Date}
  });
  
  var SeriesModel = mongoose.model('Series', seriesSchema);
  
  var instance = new SeriesModel();                   
  // Setting instance properties to some values
  SeriesModel.update({features.tvdb_id : serieData.id}, instance, {upsert: true}); 
  </code></pre>