SyncReplicasOptimizer is removed and SyncReplicasOptimizerV2 renamed to
SyncReplicasOptimizer. * `tf.zeros_initializer()` and `tf.ones_initializer()`
now return a callable that must be called with initializer arguments, in your
code replace `tf.zeros_initializer` with `tf.zeros_initializer()`. *
`SparseTensor.shape` has been renamed to `SparseTensor.dense_shape`. Same for

  }

  // We may need to allocate zero inputs for trainable dtypes we don't have JVPs
  // for. Make sure they get cleaned up.
  std::vector<Gradient*> new_zeros;
  auto delete_new_zeros = gtl::MakeCleanup([&new_zeros, this] {
    for (Gradient* tensor : new_zeros) {
      this->vspace_.DeleteGradient(tensor);
    }
  });
  std::vector<Gradient*> in_grads;
  in_grads.reserve(input_tensors.size());