OutputList dys;
  dys.reserve(y_shapes.size());
  for (const auto& y_shape : y_shapes) {
    // TODO(suharshs): This currently assumes that all y's are the same type.
    dys.push_back(
        ops::Cast(scope, ops::Const(scope, 1.0, y_shape), ys[0].type()));
  }
  OutputList dxs;
  TF_RETURN_IF_ERROR(AddSymbolicGradients(scope, ys, xs, dys, &dxs));

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