code: public static function getDisplayableAllowedValues(FixerOptionInterface $option)
      {
          $allowed = $option->getAllowedValues();
  
          if (null !== $allowed) {
              $allowed = array_filter($allowed, static function ($value) {
                  return !($value instanceof \Closure);
              });
  
              usort($allowed, static function ($valueA, $valueB) {
                  if ($valueA instanceof AllowedValueSubset) {
                      return -1;
                  }
  
                  if ($valueB instanceof AllowedValueSubset) {
                      return 1;
                  }
  
                  return strcasecmp(
                      self::toString($valueA),
                      self::toString($valueB)
                  );
              });
  
              if (0 === \count($allowed)) {
                  $allowed = null;
              }
          }
  
          return $allowed;
      }
docs: Returns the allowed values of the given option that can be converted to a string.
  
  @param FixerOptionInterface $option
  
  @return null|array