code: private function addInternalAnnotation(DocBlock $docBlock, Tokens $tokens, $docBlockIndex)
      {
          $lines = $docBlock->getLines();
          $originalIndent = $this->detectIndent($tokens, $docBlockIndex);
          $lineEnd = $this->whitespacesConfig->getLineEnding();
          array_splice($lines, -1, 0, $originalIndent.' *'.$lineEnd.$originalIndent.' * @internal'.$lineEnd);
  
          return $lines;
      }
docs: @param DocBlock $docBlock
  @param Tokens   $tokens
  @param int      $docBlockIndex
  
  @return Line[]