docs: def comments(self, case_id=None, variant_id=None, username=None):
          """Return comments for a case or variant.
  
          Args:
              case_id (str): id for a related case
              variant_id (Optional[str]): id for a related variant
          """
          logger.debug("Looking for comments")
          comment_objs = self.query(Comment)
  
          if case_id:
              comment_objs = comment_objs.filter_by(case_id=case_id)
  
          if variant_id:
              comment_objs = comment_objs.filter_by(variant_id=variant_id)
          elif case_id:
              comment_objs = comment_objs.filter_by(variant_id=None)
  
          return comment_objs