protected function handleRelations(array $fillable, Model $model, Relation $relation)
    {
        switch (true) {
        case $relation instanceof HasOne || $relation instanceof MorphOne:
            $this->updateOrCreateHasOne($fillable, $model, $relation);
            break;
        case $relation instanceof BelongsTo:
            $this->updateOrCreateBelongsToOne($fillable, $model, $relation);
            break;
        case $relation instanceof HasMany || $relation instanceof MorphMany:
            $this->updateOrCreateHasMany($fillable, $model, $relation);
            break;
        case $relation instanceof BelongsToMany || $relation instanceof MorphToMany:
            $this->updateOrCreateBelongsToMany($fillable, $model, $relation);
            break;
        }
    }