def model2subs2seqs(self) -> Dict[str, Dict[str, List[str]]]:
        model2subs2seqs = collections.defaultdict(
            lambda: collections.defaultdict(list))
        for model in self.find('sequences'):
            model_name = strip(model.tag)
            if model_name == 'node':
                continue
            for group in model:
                group_name = strip(group.tag)
                for sequence in group:
                    seq_name = strip(sequence.tag)
                    model2subs2seqs[model_name][group_name].append(seq_name)
        return model2subs2seqs