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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_alternative(self, experiment_name):
 """ Get the alternative this user is enrolled in. """

        experiment = None
        try:
            # catching the KeyError instead of using .get so that the experiment is auto created if desired
            experiment = experiment_manager[experiment_name]
        except KeyError:
            pass
        if experiment:
            if experiment.is_displaying_alternatives():
                alternative = self._get_enrollment(experiment)
                if alternative is not None:
                    return alternative
            else:
                return experiment.default_alternative
        return conf.CONTROL_GROUP