get targetCommentsKey() {
      if (self.annotationId) {
        return { annotation: self.annotationId };
      }
      if (self.draftId) {
        return { draft: self.draftId };
      }
      return null;
    }
It gets the key that indicates the target of the comment list
we should expect for the current state of stores.
Basically, it's based on the current annotation or the current draft.
@returns Record<string,string> | null