code: def sample_path(self, seed):
          
          branchset = self.root_branchset
          branch_ids = []
          while branchset is not None:
              [branch] = sample(branchset.branches, 1, seed)
              branch_ids.append(branch.branch_id)
              branchset = branch.child_branchset
          modelname = self.root_branchset.get_branch_by_id(branch_ids[0]).value
          return modelname, branch_ids
docs: Return the model name and a list of branch ids.
  
          :param seed: the seed used for the sampling