/// found, call `compute_func`. If `compute_func` set `status` to `TF_OK`,
  /// store a copy of the output parameter in the cache, and another copy in
  /// `value`.
  void LookupOrCompute(const std::string& key, T* value,
                       const ComputeFunc& compute_func, TF_Status* status) {
    if (max_age_ == 0) {
      return compute_func(key, value, status);
    }

  int num_dims;  // Must be >= -1; -1 represents unknown rank.
  int64_t* dim_sizes;
} TF_Shape;

// Add a new parameter to a TensorFlow Function.
TF_AbstractTensor* TF_AddFunctionParameter(TF_ExecutionContext* func,
                                           TF_DataType dtype, TF_Shape shape,
                                           TF_Status* s);

// Create an operation suitable to use with the provided context. The operation

// between them if `func` does not already have a gradient. If `func` already
// has a gradient different from `grad`, an error is returned.
//
// `func` must not be null.
// If `grad` is null and `func` is not in `g`, `func` is added without a
// gradient.
// If `grad` is null and `func` is in `g`, TF_GraphCopyFunction is a noop.

  // The number of devices operations run on.
  size_t num_underlying_devices() const { return underlying_devices_.size(); }

  // The devices operations run on.
  const std::vector<std::string>& underlying_devices() const {
    return underlying_devices_;
  }

  // Takes a description of a single operation being executed on the
  // ParallelDevice, and in turn runs one operation per component device with

  // available to be called/referenced by its name in this context.
  virtual Status RegisterFunction(AbstractFunction*) = 0;
  // Remove a function. 'func' argument is the name of a previously added
  // FunctionDef. The name is in fdef.signature.name.
  virtual Status RemoveFunction(const string& func) = 0;

 private:
  const AbstractContextKind kind_;
};

namespace internal {
struct AbstractContextDeleter {

// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

class Callback {
public:
	virtual ~Callback() { }
	virtual std::string run() { return "Callback::run"; }
};

class Caller {
private:
	Callback *callback_;
public:
	Caller(): callback_(0) { }
	~Caller() { delCallback(); }
	void delCallback() { delete callback_; callback_ = 0; }

TF_CAPI_EXPORT extern void TF_DefaultThreadOptions(TF_ThreadOptions* options);

// Returns a new thread that is running work_func and is identified
// (for debugging/performance-analysis) by thread_name.
//
// The given param (which may be null) is passed to work_func when the thread
// starts. In this way, data may be passed from the thread back to the caller.
//

                          const int64_t* dims, const int num_dims,
                          const char* device, TF_Status* status);
  // Dereferences the backing buffer for the variable. Note that since this can
  // fail (it runs operations), it must be called explicitly and the resulting
  // `status` checked.
  void Destroy(TFE_Context* context, TF_Status* status);

  // Reads from the variable.

        out_gradients.push_back(nullptr);
        if (build_default_zeros_grads) {
          auto func_name_it =
              FunctionsAcceptingNoneForIndicesMap()->find(trace.op_type);
          if (func_name_it == FunctionsAcceptingNoneForIndicesMap()->end() ||
              func_name_it->second.find(i) == func_name_it->second.end()) {
            zero_indices.push_back(i);
          }
        }
      } else {

TF_CAPI_EXPORT extern void TF_DeletePluggableDeviceLibraryHandle(
    TF_Library* lib_handle);

// Removes `func_name` from `g`. If `func_name` is not in `g`, an error will be
// returned.
TF_CAPI_EXPORT extern void TF_GraphRemoveFunction(TF_Graph* g,
                                                  const char* func_name,
                                                  TF_Status* status);

#ifdef __cplusplus