 
     @discardableResult
     public func logout() -> Bool {
-        return self.keychain.delete("accessToken")
+        return keychain.delete("accessToken")
     }
 
     // MARK: -

    /// - Returns: True if a session is currently available, false otherwise.

    public func isSessionValid() -> Bool {
        return self.keychain.get("accessToken") != nil
    }

    /// Ends the current session.

        var urlRequest = URLRequest(url: buildURL(for: endpoint, withParameters: parameters))
        urlRequest.httpMethod = method.rawValue

        urlSession.dataTask(with: urlRequest) { (data, _, error) in
            if let data = data {
                DispatchQueue.global(qos: .utility).async {
                    do {
