Return BMDL ratio in list of models.

def _get_bmdl_ratio(self, models):
        """Return BMDL ratio in list of models."""
        bmdls = [model.output["BMDL"] for model in models if model.output["BMDL"] > 0]

        return max(bmdls) / min(bmdls) if len(bmdls) > 0 else 0