code: public final void addBracket(SgroupBracket bracket) {
          List<SgroupBracket> brackets = getValue(SgroupKey.CtabBracket);
          if (brackets == null) {
              putValue(SgroupKey.CtabBracket,
                       brackets = new ArrayList<>(2));
          }
          brackets.add(bracket);
      }
docs: Add a bracket for this Sgroup.
  
  @param bracket sgroup bracket