PhpCsFixer\Tokenizer\Tokens::overrideAt PHP Method

    public function overrideAt($index, $token)
    {
        $this[$index]->override($token);
        $this->registerFoundToken($token);
    }

 /**
  * {@inheritdoc}
  */
 public function fix(\SplFileInfo $file, Tokens $tokens)
 {
     foreach ($tokens as $index => $token) {
         if ($token->isGivenKind(CT::T_ARRAY_INDEX_CURLY_BRACE_OPEN)) {
             $tokens->overrideAt($index, new Token('['));
         } elseif ($token->isGivenKind(CT::T_ARRAY_INDEX_CURLY_BRACE_CLOSE)) {
             $tokens->overrideAt($index, new Token(']'));
         }
     }
 }