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


        var items = [URLQueryItem]()

        let accessToken = self.keychain.get("accessToken")
        items.append(URLQueryItem(name: "access_token", value: accessToken ?? ""))

        parameters?.forEach({ parameter in

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

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

    /// Ends the current session.
