// nodes in parallel.
// in_flight_nodes_limit: when is_async is true, this value controls the
// maximum number of in flight async nodes. Enqueuing of additional async ops
// after the limit is reached blocks until some inflight nodes finishes.
// The effect is bounding the memory held by inflight TensorHandles that are
// referenced by the inflight nodes.
// A recommended value has not been established.

// TF_ImportGraphDefResults holds results that are generated by
// TF_GraphImportGraphDefWithResults().
typedef struct TF_ImportGraphDefResults TF_ImportGraphDefResults;

// Fetches the return outputs requested via
// TF_ImportGraphDefOptionsAddReturnOutput(). The number of fetched outputs is
// returned in `num_outputs`. The array of return outputs is returned in

// from a placeholder node "arg_tensor_enqueue_<tensor_id>".
//
// `tensor` is still owned by the caller. This call will be blocked if the queue
// has reached its capacity, and will be unblocked when the queued tensors again
// drop below the capacity due to dequeuing.
//
// Tensors are dequeued via the corresponding TF dequeue op.
// TODO(hongm): Add support for `timeout_ms`.

                                              TFE_TensorHandle** inputs,
                                              int num_inputs,
                                              TF_Status* status);

// Fetches the current number of inputs attached to `op`.
//
// Does not use the operation's definition to determine how many inputs should
// be attached. It is intended for use with TFE_OpGetFlatInput to inspect an

  // ForwardAccumulators, where more deeply nested accumulators should not see
  // computations from less deeply nested accumulators.
  bool BusyAccumulating() const { return call_state_.top().accumulating; }

  // Fetches the current Jacobian-vector product associated with `tensor_id`, or
  // a nullptr if none is available.
  //
  // Returns a borrowed reference, i.e. does not run VSpace::MarkAsResult on its

  // migrated to TFRT.
  //===--------------------------------------------------------------------===//
  // Clear pending nodes in thread executors and kernel caches.
  virtual void ClearCachesAndThreadExecutors() = 0;

  // Initialize the step resource container for a training step. This is used
  // in current TF runtime. For tfrt, it is used by fallback op handler.

                            char*** entries, TF_Status* status);

  /// Flushes any filesystem cache currently in memory
  ///
  /// DEFAULT IMPLEMENTATION: No op.
  void (*flush_caches)(const TF_Filesystem* filesystem);

  /// Starts a new transaction.
  ///
  /// An opaque transaction token is returned in `token`. Ownership of the token