static withId(id) {
        return this.get({
            [this.idAttribute]: id,
        });
    }
Returns a {@link Model} instance for the object with id `id`.
Returns `null` if the model has no instance with id `id`.

You can use {@link Model#idExists} to check for existence instead.

@param  {*} id - the `id` of the object to get
@throws If object with id `id` doesn't exist
@return {Model|null} {@link Model} instance with id `id`