This test code tests the upcast code:
swig_assert_equal_simple(-1, base_num2([Derived(7)]))
Although there is no explicit memory leak fix test, it does at least run the code.
Handling of None needs fixing in Python (it is working in Ruby)
Note that the Ruby implementation has a partial template specialization
for shared_ptr, whereas the Python implementation is in the generic
code!
Issue #1512
William S Fulton