// fetcher calls that the cache makes.
  calls.push_back(0);
  // Cache miss - drains an element from `calls`.
  TF_EXPECT_OK(ReadCache(&cache, "", 0, 1, &out));
  // Cache hit - does not drain an element from `calls`.
  TF_EXPECT_OK(ReadCache(&cache, "", 0, 1, &out));
  calls.push_back(block_size);
  // Cache miss followed by cache hit.
  TF_EXPECT_OK(ReadCache(&cache, "", block_size, 1, &out));

    `tf.contrib.data.Dataset.from_generator` method!
*   Fix `tf.contrib.distributions.Affine` incorrectly computing
    log-det-jacobian.
*   Fix `tf.random_gamma` incorrectly handling non-batch, scalar draws.
*   Resolved a race condition in TensorForest TreePredictionsV4Op.
*   Google Cloud Storage file system, Amazon S3 file system, and Hadoop file
    system support are now default build options.