code: public function saveFile($configuration, string $filename): bool
      {
          if (!is_writeable($filename)) {
              throw new \RuntimeException('The file "' . $filename . '" is not writeable.');
          }
  
          $content = $this->saveString($configuration);
  
          return file_put_contents($filename, $content) !== false;
      }
docs: {@inheritdoc}