**Description** The pybind11 template code and other TODO bits need updating. **TODO** - [x] Replace `PYBIND11_OVERLOAD` -> `PYBIND11_OVERRIDE` and `PYBIND11_OVERLOAD_PURE` -> `PYBIND11_OVERRIDE_PURE` : https://pybind11.readthedocs.io/en/stable/upgrade.html#v2-6 - [x] Replace `pyplusplus` in wrapper templates with `cppwg`. - [x] Add `#include <pybind11/pybind11.h>` in wrapper hpp files and remove `namespace py = pybind11;`. - [x] Remove unused code. - [x] Return strings from generators rather than appending to input strings. - [x] Fix TODOs in code.
Description
The pybind11 template code and other TODO bits need updating.
TODO
PYBIND11_OVERLOAD->PYBIND11_OVERRIDEandPYBIND11_OVERLOAD_PURE->PYBIND11_OVERRIDE_PURE: https://pybind11.readthedocs.io/en/stable/upgrade.html#v2-6pyplusplusin wrapper templates withcppwg.#include <pybind11/pybind11.h>in wrapper hpp files and removenamespace py = pybind11;.