update method
Implementation
Future update(int id,
{String? title,
String? fileName,
String? code,
String? visibility}) async {
final queryParameters = <String, dynamic>{};
if (title != null) queryParameters['title'] = title;
if (fileName != null) queryParameters['file_name'] = fileName;
if (code != null) queryParameters['code'] = code;
if (visibility != null) queryParameters['visibility'] = '$visibility';
final uri = _project
.buildUri(['snippets', '$id'], queryParameters: queryParameters);
final json = await _gitLab.request(uri, method: HttpMethod.put) as Map;
return new Snippet.fromJson(json);
}