def get_info(self, sm_id):
        """
        Extract a CompositionInfo instance containing the single
        model of index `sm_id`.
        """
        sm = self.source_models[sm_id]
        num_samples = sm.samples if self.num_samples else 0
        return self.__class__(
            self.gsim_lt, self.seed, num_samples, [sm], self.tot_weight)
Extract a CompositionInfo instance containing the single
        model of index `sm_id`.