  bool operator()(const Tensor& lhs, const Tensor& rhs) const {
    return std::less<int64>{}(lhs.scalar<int64>()(), rhs.scalar<int64>()());
  }
  bool operator()(const Tensor& lhs, const Tensor& rhs) const {
    return std::less<int64>{}(lhs.scalar<int64>()(), rhs.scalar<int64>()());
  }