convert method
Converts input and returns the result of the conversion.
Implementation
@override
String convert(Bech32 input) {
  var hrp = input.hrp;
  var data = input.data;
  if (hrp.length +
          data.length +
          separator.length +
          Bech32Validations.checksumLength >
      Bech32Validations.maxInputLength) {
    throw TooLong(
        hrp.length + data.length + 1 + Bech32Validations.checksumLength);
  }
  if (hrp.isEmpty) {
    throw TooShortHrp();
  }
  if (hasOutOfRangeHrpCharacters(hrp)) {
    throw OutOfRangeHrpCharacters(hrp);
  }
  if (isMixedCase(hrp)) {
    throw MixedCase(hrp);
  }
  hrp = hrp.toLowerCase();
  var checksummed = data + _createChecksum(hrp, data);
  if (hasOutOfBoundsChars(checksummed)) {
    throw OutOfBoundChars('<unknown>');
  }
  return hrp + separator + checksummed.map((i) => charset[i]).join();
}