You don't make it translatable in the Widget files so this is ok. In talkeditor.py you would call this line again but setting it as a translatable string by adding self.app.translate("TalkEditorApp", "... your string ...") as the parameter. See:

https://github.com/michaelbrawn/freeseer/blob/ad16feed4fb6ff97757be968632d29757380cbad/src/freeseer/frontend/talkeditor/talkeditor.py#L185