// resulting per-device and per-output TFE_TensorHandles into one
  // ParallelTensor per output of the original operation.
  //
  // Attributes are forwarded to executed operations unmodified.
  //
  // The returned optional has a value if and only if `status` evaluates to
  // TF_OK. Bad statuses are forwarded from underlying `TFE_Execute` calls, or
  // if sanity checks on dtypes/metadata fail.

// GradientDef in tensorflow/core/framework/function.proto.
//
// If successful, status is set to OK and `func` and `grad` are added to `g`.
// Otherwise, status is set to the encountered error and `g` is unmodified.
TF_CAPI_EXPORT extern void TF_GraphCopyFunction(TF_Graph* g,
                                                const TF_Function* func,
                                                const TF_Function* grad,

// Infer OpInfo::TensorProperties for graph nodes inputs/outputs.
//
// Typical use case, is to infer tensor properties from a graph, before doing
// optimization pass. Nodes modified during optimization pass have to be
// invalidated, to prevent further incorrect optimizations based on wrong shape
// and data type properties.
typedef struct TF_GraphProperties TF_GraphProperties;

  /// the block-cache-wide mu_ instance variable. The state variable should only
  /// be accessed while holding the Block's mu lock. The data vector should only
  /// be accessed after state == FINISHED, and it should never be modified.
  ///
  /// In order to prevent deadlocks, never grab the block-cache-wide mu_ lock
  /// AFTER grabbing any block's mu lock. It is safe to grab mu without locking
  /// mu_.
  struct Block {