Function as_unsigned

include/pybind11/pytypes.h:1914–1923

// unsigned type: (A)-1 != (B)-1 when A and B are unsigned types of different sizes).
template <typename Unsigned>
Unsigned as_unsigned(PyObject *o) {
    if (sizeof(Unsigned) <= sizeof(unsigned long)) {
        unsigned long v = PyLong_AsUnsignedLong(o);
        return v == static_cast<unsigned long>(-1) && PyErr_Occurred() ? (Unsigned) -1
                                                                       : (Unsigned) v;
    }
    unsigned long long v = PyLong_AsUnsignedLongLong(o);
    return v == static_cast<unsigned long long>(-1) && PyErr_Occurred() ? (Unsigned) -1
                                                                        : (Unsigned) v;
}
PYBIND11_NAMESPACE_END(detail)

class int_ : public object {