code: def get_forced_variation(self, experiment_key, user_id):
      
  
      if user_id not in self.forced_variation_map:
        self.logger.debug('User "%s" is not in the forced variation map.' % user_id)
        return None
  
      experiment = self.get_experiment_from_key(experiment_key)
      if not experiment:
        # The invalid experiment key will be logged inside this call.
        return None
  
      experiment_to_variation_map = self.forced_variation_map.get(user_id)
  
      if not experiment_to_variation_map:
        self.logger.debug('No experiment "%s" mapped to user "%s" in the forced variation map.' % (
          experiment_key,
          user_id
        ))
        return None
  
      variation_id = experiment_to_variation_map.get(experiment.id)
      if variation_id is None:
        self.logger.debug(
          'No variation mapped to experiment "%s" in the forced variation map.' % experiment_key
        )
        return None
  
      variation = self.get_variation_from_id(experiment_key, variation_id)
  
      self.logger.debug('Variation "%s" is mapped to experiment "%s" and user "%s" in the forced variation map' % (
        variation.key,
        experiment_key,
        user_id
      ))
      return variation
docs: Gets the forced variation key for the given user and experiment.
  
        Args:
          experiment_key: Key for experiment.
          user_id: The user ID.
  
        Returns:
          The variation which the given user and experiment should be forced into.