         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()


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

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