def _get_cluster_sizes(self):
        """
        Returns the marker size (in points, e.g. area of the circle) based on
        the scores, using the prop_to_size scaling mechanism.
        """
        # NOTE: log and power are hardcoded, should we allow the user to specify?
        return prop_to_size(
            self.scores_, mi=self.min_size, ma=self.max_size, log=False, power=0.5
        )