anchor.diff:      return client.slash("users").all(headers: authorizationHeader);
     }
     
  -  bool get isLoggedIn => null != _token;
  +  bool get isLoggedIn => null != token;
     bool get hasPrivateKey => null != _private;
     
     void checkLoggedIn() {
  
positive.code:         body: {"username" : username,
                 "password" : password}).then((response) {
        checkResponse(response, 201);
        return _token = JSON.decode(response.body)["api_token"];
      });
    }
    
  
negative.code: 
  class DuseClient {
    final RestClient client;
    String token;
    KeyPair _private;
    
    DuseClient(Uri baseUri, ClientFactory clientFactory)
        : client = initializeClient(baseUri, clientFactory);
    
    Map<String, String> get authorizationHeader =>
        {"authorization": token};
    
    static RestClient initializeClient(Uri baseUri,
                                       ClientFactory clientFactory) {
  