Non-throwing cast

[VelocityRa]

I often declare methods/functions that contain arguments with multiple possible types (Union/std::variant), so I often use this pattern, many layers deep and/or with chained checks.
Assume the following code is in a def func/method lambda:

if (py::isinstance<MyType>(arg)) {
    MyType* obj = py::cast<MyType*>(arg);
    // ...
}

This is more verbose code-wise and presumably duplicates work for no reason.
If there was a non-throwing py::cast variant (that returned ie. nullptr/std::nullopt on failure) we could just do:

if (MyType* obj = py::cast<MyType*>(arg) {
    // ...
}

but there is none, and throwing exceptions is expensive / not recommended for non-exceptional program logic.

Note: I use a user-defined type MyType here (and specifically casting to a pointer), but this should of course also work for pybind11 C++ Python API types like py::int_ (I suppose it should not cast to a pointer in these cases).