def save(self, doc):
        if doc.id:
            return self.update(doc)
        else:
            return self.insert(doc)
def _restore_vars(v_list, t_list):
  """Restore variables in v_list from t_list."""
  ops = []
  for v, t in zip(v_list, t_list):
    ops.append(v.assign(t))
  return ops