// 'ab...c' and shape of rank 10; the range [3:-1] denotes the broadcasted
  // axes.
  int bx_start, by_start;
  absl::optional<int> bx_end, by_end;
  std::tie(bx_start, bx_end) = EinsumGetBcastSubshape(x_subs);
  std::tie(by_start, by_end) = EinsumGetBcastSubshape(y_subs);

  // Sum the gradient across the broadcasted axes.
  auto args = internal::BroadcastGradientArgs(
      scope, Slice1dHelper(scope, x_shape, bx_start, bx_end),