// executed in sequence. Assigning nodes to different executors allows executing
// 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

// into python now.
template <typename Gradient, typename BackwardFunction, typename TapeTensor>
class VSpace {
 public:
  virtual ~VSpace() {}

  // Returns the number of elements in the gradient tensor.
  virtual int64_t NumElements(Gradient* tensor) const = 0;

  // Consumes references to the tensors in the gradient_tensors list and returns
  // a tensor with the result.

    TF_Status* status);

// ----------------------------  PJRT  -----------------------------------------
// Passes the pointer to a vector of PJRT_NamedValue and number of options to
// set options for creating a PJRT client. Passes nullptr for create_options and
// 0 for num_options if no options need to be set. You can use
// ConvertToPjRtNamedValueList in