code: function(models, options) {
      if(!models) return false;
      this.remove(models, options);
      var singular = !_.isArray(models);
      models = singular ? [models] : _.clone(models);
      return this._callAdapter('removeFromIndex', options, models);
    }
docs: Removes a model's key from index
  @param {Array} models   model(s) whose keys (ids) are removed from index
  @param {Object} options options
  @returns {Promise} promise