private static Set<String> getRequiredFields(JsonNode node) {
    JsonNode requiredList = node.get("required");
    if (requiredList == null || (!requiredList.isArray() && requiredList.size() == 0)) return Collections.emptySet();
    Set<String> result = new TreeSet<>();
    for (JsonNode element : requiredList) {
      if (element.isTextual()) {
        result.add(element.asText());
      }
    }
    return result;
  }
private static Set<String> getRequiredFields(JsonNode node)