code: public boolean isValidLogin()
    {
      String userToken = UserTokenStorageFactory.instance().getStorage().get();
      if( userToken != null && !userToken.equals( "" ) )
      {
        return Invoker.<Boolean>invokeSync( USER_MANAGER_SERVER_ALIAS, "isValidUserToken", new Object[] { userToken } );
      }
      else
      {
        return CurrentUser() != null;
      }
    }
docs: if user token has been saved from previous logins, the method checks if the user token is still valid;
  if user token is not saved, but user logged in, the method checks if the user session is still valid
  
  @return true, if user token is valid or user is logged in, else false