fetch static method
returns the document in collection
with id
throws UnsupportedError if user has no access rights or document ist does not exist
Implementation
static Future<ParseDocument> fetch(String collection, String id) async {
var response = await http.get('$_url/parse/classes/$collection/$id',
headers: _headers);
_errorHandler(response);
return ParseDocument(
response.body, response.statusCode == 200, null, collection);
}