docs: @Nullable
    public static List<LbConfig> getChildPolicyFromXdsConfig(LbConfig xdsConfig) {
      Map<String, ?> map = xdsConfig.getRawConfigValue();
      List<?> rawChildPolicies = getList(map, XDS_CONFIG_CHILD_POLICY_KEY);
      if (rawChildPolicies != null) {
        return unwrapLoadBalancingConfigList(checkObjectList(rawChildPolicies));
      }
      return null;
    }