code: protected function createConfigurationDefinition()
      {
          $default = [
              'this' => '$this',
              '@this' => '$this',
              '$self' => 'self',
              '@self' => 'self',
              '$static' => 'static',
              '@static' => 'static',
          ];
  
          return new FixerConfigurationResolverRootless('replacements', [
              (new FixerOptionBuilder('replacements', 'Mapping between replaced return types with new ones.'))
                  ->setAllowedTypes(['array'])
                  ->setNormalizer(static function (Options $options, $value) use ($default) {
                      $normalizedValue = [];
                      foreach ($value as $from => $to) {
                          if (\is_string($from)) {
                              $from = strtolower($from);
                          }
  
                          if (!isset($default[$from])) {
                              throw new InvalidOptionsException(sprintf(
                                  'Unknown key "%s", expected any of "%s".',
                                  \is_object($from) ? \get_class($from) : \gettype($from).(\is_resource($from) ? '' : '#'.$from),
                                  implode('", "', array_keys($default))
                              ));
                          }
  
                          if (!\in_array($to, self::$toTypes, true)) {
                              throw new InvalidOptionsException(sprintf(
                                  'Unknown value "%s", expected any of "%s".',
                                  \is_object($to) ? \get_class($to) : \gettype($to).(\is_resource($to) ? '' : '#'.$to),
                                  implode('", "', self::$toTypes)
                              ));
                          }
  
                          $normalizedValue[$from] = $to;
                      }
  
                      return $normalizedValue;
                  })
                  ->setDefault($default)
                  ->getOption(),
          ], $this->getName());
      }
docs: {@inheritdoc}