Most of the API code is generated from the ZAP java source code.
To regenerate the API code you will need the repos zaproxy and zap-extensions checked out at the same level as this one.
You should typically generate the core API calls from the latest release tag e.g.:
cd zaproxy
git fetch upstream -t
git checkout tags/v2.13.0
./gradlew generatePythonApiEndpoints
cd ..
The add-on APIs can be generated from the zap-extensions main branch:
cd zap-extensions
git pull upstream main
./gradle generatePythonZapApiClientFiles --continue
cd ..
The above commands will update the files in src/zapv2.
If any new files are created then they should be manually added to src/zapv2/__init__.py as per the existing files.
Note that you should also update the CHANGELOG.md file to state whatever has been changed.