             urlRequest.httpMethod = httpMethod
             
             var oauthItems = ["oauth_callback": callback]
+            
+            // TODO: xAuth
             
             let authorizationHeader = try self.authorizationHeader(oauthItems: oauthItems, HTTPMethod: httpMethod, url: url, consumerKey: session.consumerKey, consumerSecret: session.consumerSecret)
             

        case ReverseAuth
    }
    
    public class func requestRequestToken(session: Session, xAuthMode: xAuthMode?, callback: String, handler: @escaping (String?, String?, NSError?) -> Void) {
        guard let url = URL.twitterOAuthURL(endpoint: "request_token") else {
            handler(nil, nil, Error.unknown)
            return

                    return
                }
                
                do {
                    let (token, tokenSecret) = try self.processOAuth(response: response, data: data)
                    
                    handler(token, tokenSecret, nil)
                }
                catch let error as NSError {
                    handler(nil, nil, error)
                }
                catch {
                    handler(nil, nil, Error.unknown)
                }
            })
            task.resume()
        }
