code: function save(model) {
        var _this = this;
        var record = this.records.get(model);
        model = record || this._ensureModel(model);
        return Promise.resolve(model.save()).then(function () {
          if (!record) {
            _this.insert(model);
          }
          return model;
        });
      }
docs: Save a model to the server.
  
  @public
  @instance
  @method save
  @memberOf Storage
  @param {Number|String|Object|Backbone.Model} model - The model to save
  @returns {Promise} - A promise that will resolve to the saved model.