public static List<Code> getSubsumes(ValueSetDefineConceptComponent c) {
    List<Code> res = new ArrayList<Code>();

    for (Extension e : c.getExtensions()) {
      if (EXT_SUBSUMES.equals(e.getUrlSimple())) res.add((Code) e.getValue());
    }
    return res;
  }
 public static void addSubsumes(ValueSetDefineConceptComponent nc, String code) throws Exception {
   nc.getModifierExtensions().add(Factory.newExtension(EXT_SUBSUMES, Factory.newCode(code), true));
 }