message: Fix compilation of the python binding
diff: @@ -99,7 +99,7 @@ void register_class(atom_value*, pybind11::module& m,
  auto cmp = [](atom_value x, atom_value y) {
  return x == y;
  };
  - std::string (*to_string_fun)(const atom_value&) = &to_string;
  + std::string (*to_string_fun)(atom_value) = &to_string;
  pybind11::class_<atom_value>(m, name.c_str())
  .def("__str__", to_string_fun)
  .def("__repr__", repr_fun)
  