To verify, you have saved these changes and restarted the game? Changes to the script only take effect on next start of the game. I see no issues with the code.
It could be the editor causing problems as gdscript can be whitespace sensitive, though generally so long as the number of tabs are correct then the number of spaces that represent the tabs should be irrelevant. As far as I know, some files use 2 spaces for tabs, but most use 4. If it doesn't work you may need to use the bugfix I posted in the mods channel of Discord.
Edit: traits.gd seems to use 2 spaces instead of tabs, Sublime Text interpreted that as 2 spaces for tabs. The rest of files just use tabs, not spaces. So the number of spaces that represents a tab is left to the editor.