def insert(self, doc, synced=False):
        doc.id = self.get_next_id()
        doc.synced = synced
        try:
            self.db.docs.insert(doc)
        except Exception as e:
            raise DatabaseException(e)
        return doc
def _copy_vars(v_list):
  """Copy variables in v_list."""
  t_list = []
  for v in v_list:
    t_list.append(tf.identity(v))
  return t_list