code: function(layerModel, gmapsLayer, gmapsMap) {
    this.gmapsLayer = gmapsLayer;
    this.map = this.gmapsMap = gmapsMap;
    this.model = layerModel;
    this.model.bind('change', this._update, this);
  
    this.type = layerModel.get('type') || layerModel.get('kind');
    this.type = this.type.toLowerCase();
  }
docs: base layer for all google maps