public Configuration getDefaultConfig() {
    Configuration config = getConfiguration();
    config.getProperties().values().forEach(
      each -> each.values().removeIf(Objects::isNull)
    );
    return config;
  }
@return default configuration of the stack, with some updates necessary so that the config can be applied
(eg. some properties need a unit to be appended)
ambari-server/src/main/java/org/apache/ambari/server/controller/internal/Stack.java