code: @Nullable
    public static List<LbConfig> getFallbackPolicyFromXdsConfig(LbConfig xdsConfig) {
      Map<String, ?> map = xdsConfig.getRawConfigValue();
      List<?> rawFallbackPolicies = getList(map, XDS_CONFIG_FALLBACK_POLICY_KEY);
      if (rawFallbackPolicies != null) {
        return unwrapLoadBalancingConfigList(checkObjectList(rawFallbackPolicies));
      }
      return null;
    }
docs: Extracts list of fallback policies from xds loadbalancer config.