docs: def variant(case_id, variant_id):
      """Show a single variant."""
      case_obj = app.db.case(case_id)
      variant = app.db.variant(case_id, variant_id)
      if variant is None:
          return abort(404, "variant not found")
  
      comments = app.db.comments(variant_id=variant.md5)
      template = 'sv_variant.html' if app.db.variant_type == 'sv' else 'variant.html'
      return render_template(template, variant=variant, case_id=case_id,
                             comments=comments, case=case_obj)