message: Use the function required by PackedDistributedVariable to return the primary variable.
diff: @@ -1324,7 +1324,7 @@ class OnReadPolicy(VariablePolicy):
  def _get_cross_replica(self, var):
  if self._aggregation == vs.VariableAggregation.ONLY_FIRST_REPLICA:
  - return var._primary # pylint: disable=protected-access
  + return var._get_replica(0) # pylint: disable=protected-access
  with ds_context.enter_or_assert_strategy(var.distribute_strategy):
  return var.distribute_strategy.reduce(
  