login function Null safety

Future<Login?> login(
  1. String username,
  2. String password
)

Implementation

Future<Login?> login(String username, String password) async {
  var response = await loginResponse(username, password);
  var headers = response.headers;
  if (headers['x-ratelimit-remaining'] == '0') {
    print('Rate Limit Exceeded.');
  } else {
    return Login.fromJson(jsonDecode(response.body));
  }
}