1. override
Future<Response> patch(url, { Map<String, String> headers, body, Encoding encoding })

Sends an HTTP PATCH request with the given headers and body to the given URL, which can be a Uri or a String.

body sets the body of the request. It can be a String, a List<int> or a Map<String, String>. If it's a String, it's encoded using encoding and used as the body of the request. The content-type of the request will default to "text/plain".

If body is a List, it's used as a list of bytes for the body of the request.

If body is a Map, it's encoded as form fields using encoding. The content-type of the request will be set to "application/x-www-form-urlencoded"; this cannot be overridden.

encoding defaults to UTF-8.

For more fine-grained control over the request, use send instead.

Source 

@override
Future<Response> patch(dynamic url, {Map<String, String> headers, dynamic body,
    Encoding encoding}) =>
  _sendUnstreamed("PATCH", url, headers, body, encoding);