src/Node.php
protected function isSourceAttribute($key)
    {
        $modelName = source_model_name($this->getNodeTypeName(), true);

        return in_array($key, call_user_func([$modelName, 'getSourceFields']));
    }
protected function isSourceAttribute($key)
    {
        $modelName = source_model_name($this->getNodeTypeName(), true);

        return in_array($key, call_user_func([$modelName, 'getSourceFields']));
    }
protected function isSourceAttribute ( $ key ) { $ modelName = source_model_name ( $ this -> getNodeTypeName ( ) , true ) ; return in_array ( $ key , call_user_func ( [ $ modelName , 'getSourceFields' ] ) ) ; }
Checks if a key is a node source attribute

@param $key
@return bool
Checks if a key is a node source attribute