src/Versatile/Query/Builder.php
public function isRelation($key)
    {
        if(!method_exists($this->model, $key)) {
            return false;
        }
        $relation = $this->model->{$key}();
        return ($relation instanceof Relation);
    }
public function isRelation($key)
    {
        if(!method_exists($this->model, $key)) {
            return false;
        }
        $relation = $this->model->{$key}();
        return ($relation instanceof Relation);
    }
Check if a key is a relation

@param string $key
@return bool