     
     /**
         One can create custom logger to process all errors and responses in one place.
-        Main purpose is to debug or track all the errors accured in framework via some analytic tool.
+        Main purpose is to debug or to track all the errors accured in framework via some analytic tool.
     */
     public var logger       : Logger?
     


    private func deathorizeAndNotify() {
        self.deauthorize()
    }
    
}

        return _sharedSession!
    }
    
    /** Whether session is authorized or not. */
    public func isAuthorized() -> Bool {
        let keychain = Keychain(configuration: self.configuration)
        let (accessToken, _) = keychain.accessToken()
        return accessToken != nil
    }
    
    /** 
        Removes access token from keychain.
        This method Doesn't post `QuadratSessionDidBecomeUnauthorizedNotification`. 
    */
    public func deauthorize() {
        let keychain = Keychain(configuration: self.configuration)
        keychain.deleteAccessToken()
