docs: def check_work_done(self, grp):
          """
          Check for the existence of alignment and result files.
          """
          id_ = self.get_id(grp)
          concat_file = os.path.join(self.cache_dir, '{}.phy'.format(id_))
          result_file = os.path.join(self.cache_dir, '{}.{}.json'.format(id_, self.task_interface.name))
          return os.path.exists(concat_file), os.path.exists(result_file)