code: static boolean isNestedArrayPattern(Node n) {
      checkState(n.isArrayPattern());
      for (Node key = n.getFirstChild(); key != null; key = key.getNext()) {
        if (key.hasChildren()) {
          return true;
        }
      }
      return false;
    }
docs: Determine whether the destructuring array pattern is nested
  
  @param n array pattern node