def get_variation_for_experiment(self, experiment_id):
    """ Helper method to retrieve variation ID for given experiment.

    Args:
      experiment_id: ID for experiment for which variation needs to be looked up for.

    Returns:
      Variation ID corresponding to the experiment. None if no decision available.
    """

    return self.experiment_bucket_map.get(experiment_id, {self.VARIATION_ID_KEY: None}).get(self.VARIATION_ID_KEY)
Helper method to retrieve variation ID for given experiment.

    Args:
      experiment_id: ID for experiment for which variation needs to be looked up for.

    Returns:
      Variation ID corresponding to the experiment. None if no decision available.