Deriving classes from virtual classes and using a factory function seems not to work

[tenspd137]

Hi all - I am trying to export an abstract base class, derive a class from it in python and create from a factory function. I get the following error:
TypeError: pybind11::init(): construction failed: returned holder-wrapped instance is not an alias instance

Here is an example that recreates the problem:
Test.hpp

#pragma once

#include <pybind11/pybind11.h>

namespace py = pybind11;

void export_test(py::module& m);

Test.cpp

#include "Test.hpp"
#include <memory>

class Base
{
public:
    virtual ~Base() = default;
    virtual int Add(int input) const = 0;
};

class Derived1 : public Base
{
public:
    virtual ~Derived1() = default;
    int Add(int input) const override
    {
        return input + 1;
    }
};

class Derived2 : public Base
{
public:
    virtual ~Derived2() = default;
    int Add(int input) const override
    {
        return input + 2;
    }
};

std::unique_ptr<Base> SelectDerived(int select)
{
    if(select == 1)
    {
        return std::unique_ptr<Base>(new Derived1());
    }
    else
        return std::unique_ptr<Base>(new Derived2());
}

template <typename BaseClass = Base>
class pyBase : public BaseClass
{
public:
    using BaseClass::BaseClass;

    int Add(int input) const override
    {
        PYBIND11_OVERRIDE_PURE(int, BaseClass, Add, input);
    }
};

void export_test(py::module& m)
{
    auto test = py::class_<Base, pyBase<>>(m, "Base");
    test.def(py::init([](int select) { return SelectDerived(select); }));
}

PYBIND11_MODULE(example, m)
{
    export_test(m);
}

And finally in python: (inside a jupyter notebook)

import example.Base as Base
class pyBase(Base):
    def __init__(self, selection):
        super().__init__(selection)
        self.added_info = "More Stuff"
 q = pyBase(1)
 ---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Input In [39], in <cell line: 1>()
----> 1 q = pyBase(1)

Input In [38], in pyBase.__init__(self, selection)
      2 def __init__(self, selection):
----> 3     super().__init__(selection)
      4     self.added_info = "More Stuff"

TypeError: pybind11::init(): construction failed: returned holder-wrapped instance is not an alias instance

Basically, how do I expose my Base class and obtain an object of a derived class from a C++ factory function?

Thanks for any help - I am really stuck.