message: [TF] tf.test.TestCase.setUp resets the default summary writer.
  This fixues graph leaks caused by tests that call writer.set_as_default().
diff: @@ -1598,6 +1598,9 @@ class TensorFlowTestCase(googletest.TestCase):
  ops._default_graph_stack.reset() # pylint: disable=protected-access
  ops.reset_default_graph()
  random_seed.set_random_seed(random_seed.DEFAULT_GRAPH_SEED)
  + # Reset summary writer in case another test used set_as_default() with their
  + # summary writer.
  + context.context().summary_writer = None
  # Avoiding calling setUp() for the poorly named test_session method.
  if self.id().endswith(".test_session"):
  