code: def is_authenticated(self):
          
          if self._proxy is None:
              return False
          elif self._proxy.has_authentication():
              return self._proxy.get_authentication().is_valid()
          else:
              return False
docs: Tests if an agent is authenticated to this session.
  
          return: (boolean) - true if valid authentication credentials
                  exist, false otherwise
          compliance: mandatory - This method must be implemented.