Set the variant for a specific user and mark a participation for the
        experiment.

        Participation will *only* be marked for visitors who have been verified
        as humans (to avoid skewing reports with requests from bots and web
        crawlers).

def participate(self, identity, experiment_name, variant):
        """
        Set the variant for a specific user and mark a participation for the
        experiment.

        Participation will *only* be marked for visitors who have been verified
        as humans (to avoid skewing reports with requests from bots and web
        crawlers).
        """
        self.set_variant(identity, experiment_name, variant)
        if self.is_verified_human(identity):
            self.mark_participant(experiment_name, variant)