RequestOptions constructor
      
      RequestOptions({ 
    
    
- String path = '',
- dynamic data,
- ProgressCallback? onReceiveProgress,
- ProgressCallback? onSendProgress,
- CancelToken? cancelToken,
- String? method,
- Duration? sendTimeout,
- Duration? receiveTimeout,
- Duration? connectTimeout,
- Map<String, dynamic> ? queryParameters,
- String? baseUrl,
- Map<String, dynamic> ? extra,
- Map<String, dynamic> ? headers,
- bool? preserveHeaderCase,
- ResponseType? responseType,
- String? contentType,
- ValidateStatus? validateStatus,
- bool? receiveDataWhenStatusError,
- bool? followRedirects,
- int? maxRedirects,
- bool? persistentConnection,
- RequestEncoder? requestEncoder,
- ResponseDecoder? responseDecoder,
- ListFormat? listFormat,
- bool? setRequestContentTypeWhenNoPayload,
- StackTrace? sourceStackTrace,
Implementation
RequestOptions({
  this.path = '',
  this.data,
  this.onReceiveProgress,
  this.onSendProgress,
  this.cancelToken,
  super.method,
  super.sendTimeout,
  super.receiveTimeout,
  Duration? connectTimeout,
  Map<String, dynamic>? queryParameters,
  String? baseUrl,
  super.extra,
  super.headers,
  super.preserveHeaderCase,
  super.responseType,
  super.contentType,
  super.validateStatus,
  super.receiveDataWhenStatusError,
  super.followRedirects,
  super.maxRedirects,
  super.persistentConnection,
  super.requestEncoder,
  super.responseDecoder,
  super.listFormat,
  bool? setRequestContentTypeWhenNoPayload,
  StackTrace? sourceStackTrace,
}) : assert(connectTimeout == null || !connectTimeout.isNegative) {
  this.sourceStackTrace = sourceStackTrace ?? StackTrace.current;
  this.queryParameters = queryParameters ?? {};
  this.baseUrl = baseUrl ?? '';
  this.connectTimeout = connectTimeout;
}