serialize method

Implementation

Future<MultiPartBodySerializationResult> serialize() async {
  final boundary =
      this.boundary ?? getRandomBoundaryString(random ?? Random());
  final partsList = await parts.toList();
  return MultiPartBodySerializationResult(
    contentLength: contentLength(partsList, boundary),
    bodyBytesStream: bodyBytesStream(partsList, boundary),
    boundary: boundary,
  );
}