/**
  * {@inheritdoc}
  */
 public function hasExtraKeys(Expression $expr = null)
 {
     if (!$expr) {
         return $this->rootPackageFile->hasExtraKeys();
     }
     foreach ($this->rootPackageFile->getExtraKeys() as $key => $value) {
         if ($expr->evaluate($key)) {
             return true;
         }
     }
     return false;
 }