code: public EList<RuleElement> getGroups()
    {
      if (groups == null)
      {
        groups = new EObjectContainmentEList<RuleElement>(RuleElement.class, this, SimpleAntlrPackage.ALTERNATIVES__GROUPS);
      }
      return groups;
    }
docs: <!-- begin-user-doc -->
  <!-- end-user-doc -->
  @generated