public function addRelation($columnName)
    {
        $relationName = getRelationName($columnName);

        if (
            ! array_key_exists($relationName, $this->relations) &&
            ! in_array($relationName, $this->relations)
        ) {
            $methodName = camel_case('laratables_'.$relationName.'relation_query');
            if (method_exists($this->class, $methodName)) {
                $this->relations[$relationName] = $this->class::$methodName();

                return;
            }

            $this->relations[] = $relationName;
        }
    }