message: Fix bug in handling of SAVERS collection for shutdown hook.
diff: @@ -292,14 +292,21 @@ class GracefulShutdownHook(session_run_hook.SessionRunHook):
  if self._saver:
  return self._saver
  - savers = ops.get_collection(ops.GraphKeys.SAVERS)[0]
  + savers = ops.get_collection(ops.GraphKeys.SAVERS)
  if not savers:
  return None
  if not isinstance(savers, list):
  return savers
  - assert len(savers) == 1, 'Only one saver supported.'
  + if len(savers) > 1:
  + logging.error(
  + 'Multiple savers in the SAVERS collection. On-demand checkpointing '
  + 'will be disabled. Pass an explicit `saver` to the constructor to '
  + 'override this behavior.'
  + )
  + return None
  +
  return savers[0]
  def after_run(self, run_context, run_values):
  