code: protected function applyFix(\SplFileInfo $file, Tokens $tokens)
      {
          // figure out where the comment should be placed
          $headerNewIndex = $this->findHeaderCommentInsertionIndex($tokens);
  
          // check if there is already a comment
          $headerCurrentIndex = $this->findHeaderCommentCurrentIndex($tokens, $headerNewIndex - 1);
  
          if (null === $headerCurrentIndex) {
              if ('' === $this->configuration['header']) {
                  return; // header not found and none should be set, return
              }
  
              $this->insertHeader($tokens, $headerNewIndex);
          } elseif ($this->getHeaderAsComment() !== $tokens[$headerCurrentIndex]->getContent()) {
              $tokens->clearTokenAndMergeSurroundingWhitespace($headerCurrentIndex);
              if ('' === $this->configuration['header']) {
                  return; // header found and cleared, none should be set, return
              }
  
              $this->insertHeader($tokens, $headerNewIndex);
          } else {
              $headerNewIndex = $headerCurrentIndex;
          }
  
          $this->fixWhiteSpaceAroundHeader($tokens, $headerNewIndex);
      }
docs: {@inheritdoc}