`nix develop` fails on example `python-local-development` (source location of dependency does not exist)

[akaihola]

I get the following error when running nix develop on current main in the examples/packages/languages/python-local-development/ directory:

[~/dream2nix/examples/packages/languages/python-local-development]$ nix develop
Error: The python dependency charset-normalizer of mytool is configured to be installed in editable mode,
but the provided source location
/home/akaihola/dream2nix/examples/packages/languages/python-local-development/.editables/charset_normalizer
does not exist.
Please provide a path to a local copy of the source code of charset-normalizer.

I can't find documentation on how I'm supposed to manage editable dependencies. Do I need to download the source distribution for each of the editable dependencies (just charset-normalizer in this case) and extract them into ./.editables/? Or is there some tooling to manage this? It would be helpful if this was pointed out in the documentation and in the error message.