pybind11 usually casts base-class references or pointers to the most-derived wrapped type, using RTTI and dynamic casts. This does not seem to work for Table and Record objects, where we instead have to wrap derived-class accessors that return the appropriate type.

I suspect this is because the true types are defined in anonymous namespaces in C++ files, so the most-derived types are not actually accessible to pybind11, and it's doing some sort of dict lookup on std::type_info rather than a tree of dynamic_casts (what Boost.Python did). If that's the case, a invisible change to how these classes are implemented could clean up our pybind11 wrappers. I imagine we wouldn't want to try to fix this upstream, as pybind11's approach is almost certainly faster than Boost.Python's and works as well in the vast majority of cases.