}  // namespace ops

// Macros used to define gradient functions for ops.
#define REGISTER_GRADIENT_OP(name, fn) \
  REGISTER_GRADIENT_OP_UNIQ_HELPER(__COUNTER__, name, fn)

#define REGISTER_NO_GRADIENT_OP(name) \
  REGISTER_GRADIENT_OP_UNIQ_HELPER(__COUNTER__, name, nullptr)

#define REGISTER_GRADIENT_OP_UNIQ_HELPER(ctr, name, fn) \
  REGISTER_GRADIENT_OP_UNIQ(ctr, name, fn)

#define REGISTER_GRADIENT_OP_UNIQ(ctr, name, fn) \