Not working well with python-docstring-highlighter

Hi, I installed https://github.com/rodolphebarbanneau/python-docstring-highlighter and it doesn't seem to work with this theme.
Not sure if that extensions uses non-standard highlight group definitions (or whatever this is called in vscode), or this theme not providing them.

See Dark Modern:

vs. Dracula Soft:

Most other themes I sampled do work, so I guess this can be solved at the theme level.