code: public function convert($string, $to_encoding, $from_encoding = null)
      {
          $from_encoding = (null !== $from_encoding) ? $from_encoding : $this->resolveInputEncoding($string);
  
          $result = mb_convert_encoding($string, $to_encoding, $from_encoding);
  
          if (false === $result) {
              throw EncodingConversionFailureException::forStringAndEncodings($string, $from_encoding, $to_encoding);
          }
  
          return $result;
      }
docs: {@inheritDoc}
  
  A list of supported encodings can be determined by running
  {@link http://php.net/manual/en/function.mb-list-encodings.php `mb_list_encodings()`}