docs: def add_comment(self, case_obj, text, variant_id=None, username=None):
          """Add a comment to a variant or a case"""
  
          comment = Comment(
              text=text,
              username=username or 'Anonymous',
              case=case_obj,
              # md5 sum of chrom, pos, ref, alt
              variant_id=variant_id
          )
          self.session.add(comment)
          self.save()
          return comment