patch abstract method
Send a PATCH request.
If uri is given, the request will be sent to that exact uri. If uri is
null, the uri on the BaseRequest will be used (and is thus required).
If headers are given, they will be merged with the set of headers
already defined on the BaseRequest.
If body is given, it must be of valid type for the type of request being
sent. For example, if sending a JSON request using the JsonRequest,
body must be a JSON-encodable Map or List.
Implementation
Future<Response> patch(
{dynamic body, Map<String, String>? headers, Uri? uri});