Upload anh bang POST in flutter

static dynamic upImage(File imageFile) async {
  var stream = new http.ByteStream(DelegatingStream.typed(imageFile.openRead()));  var length = await imageFile.length();  final String token = await constants.getToken();  var uri = Uri.parse(apiupload);
  Map<String, String> headers = {
    'se-client': "api",    'se-api-key': "f50949f7a35a3b0d46b08abd20bead1d:hd2OQtdb5Z9SCx5OAF7iKi97G8PsBJbX9YjIbYVHufDo4nVCycsJHvmPoXuRfVgv",    'se-viewer-token': token
  };  Map<String, String> body = {
    'typeId': 'image',    'productId': '@SE/Media',  };  var multipartFile = new http.MultipartFile('file', stream, length,filename: basename( imageFile.path));
  var request = new http.MultipartRequest("POST", uri);  request.headers.addAll(headers);  request.fields.addAll(body);  request.files.add(multipartFile);
  var response = await request.send();  return  await response.stream.bytesToString();}