// once unless the tape is persistent) and produces the gradient of the target
  // tensors with respect to the source tensors. The output gradients are used
  // if not empty and not null. The result is populated with one tensor per
  // target element.
  Status ComputeGradient(
      AbstractContext* ctx, absl::Span<AbstractTensorHandle* const> targets,
      absl::Span<AbstractTensorHandle* const> sources,

                     uint64* file_size) override;
  Status RenameFile(const std::string& src, const std::string& target,
                    TransactionToken* token) override;
  Status CopyFile(const std::string& src, const std::string& target,
                  TransactionToken* token) override;
  std::string TranslateName(const std::string& name) const override;

  tensorflow::mutex lock;
};

#if !defined(IS_MOBILE_PLATFORM) && !defined(IS_SLIM_BUILD)
struct TF_Server {
  TF_Server(std::unique_ptr<tensorflow::ServerInterface> server);

  const tensorflow::string target;
  std::unique_ptr<tensorflow::ServerInterface> server;
};
#endif  // !defined(IS_MOBILE_PLATFORM) && !defined(IS_SLIM_BUILD)

namespace tensorflow {

// Set the shapes and types of the output's handle.
//