protected @Nullable <T> T findChildByClass(Class<T> aClass) {
    for (PsiElement cur = getFirstChild(); cur != null; cur = cur.getNextSibling()) {
      if (aClass.isInstance(cur)) return (T)cur;
    }
    return null;
  }
protected @Nullable <T> T findChildByClass(Class<T> aClass)