std::vector<char> out;
  TF_EXPECT_OK(ReadCache(&cache1, want_filename, want_offset, want_n, &out));
  EXPECT_EQ(calls, 1);
  TF_EXPECT_OK(ReadCache(&cache2, want_filename, want_offset, want_n, &out));
  EXPECT_EQ(calls, 2);
  TF_EXPECT_OK(ReadCache(&cache3, want_filename, want_offset, want_n, &out));
  EXPECT_EQ(calls, 3);
  TF_EXPECT_OK(ReadCache(&cache4, want_filename, want_offset, want_n, &out));

  cache2.LookupOrCompute("b", &value, compute_func, &status);
  TF_EXPECT_OK(status.status);
  EXPECT_EQ(value, 1);
  EXPECT_EQ(num_compute_calls, 2);
  cache2.LookupOrCompute("c", &value, compute_func, &status);
  TF_EXPECT_OK(status.status);
  EXPECT_EQ(value, 2);
  EXPECT_EQ(num_compute_calls, 3);
  cache2.LookupOrCompute("d", &value, compute_func, &status);
  TF_EXPECT_OK(status.status);
  EXPECT_EQ(value, 3);

    graph optimizer options are now specified via
    `GraphOptions.OptimizerOptions`.
*   `ASSERT_OK` / `EXPECT_OK` macros conflicted with external projects, so they
    were renamed `TF_ASSERT_OK`, `TF_EXPECT_OK`. The existing macros are
    currently maintained for short-term compatibility but will be removed.
*   The non-public `nn.rnn` and the various `nn.seq2seq` methods now return just