code: protected function applyFix(\SplFileInfo $file, Tokens $tokens)
      {
          for ($index = $tokens->count() - 1; 0 <= $index; --$index) {
              if (!$tokens[$index]->isGivenKind(T_CLASS) || !$this->isClassCandidate($tokens, $index)) {
                  continue;
              }
  
              // make class final
              $tokens->insertAt(
                  $index,
                  [
                      new Token([T_FINAL, 'final']),
                      new Token([T_WHITESPACE, ' ']),
                  ]
              );
          }
      }
docs: {@inheritdoc}