apollo-client/src/main/java/com/ctrip/framework/apollo/util/yaml/YamlParser.java/YamlParser/getFlattenedMap
class YamlParser:  private Map<String, Object> getFlattenedMap(Map<String, Object> source) {
    Map<String, Object> result = new LinkedHashMap<>();
    buildFlattenedMap(result, source, null);
    return result;
  }