private static List<String> extractErrors(List<ResolveResult> results) {
        List<String> errors = List.of();
        for (ResolveResult result : results) {
            if (result.errorMsg() != null) {
                if (errors.isEmpty()) {
                    errors = new ArrayList<>();
                }
                errors.add(result.errorMsg());
            }
        }
        return errors;
    }
The name of the query property containing the source name added to the query to each source by this
container-search/src/main/java/com/yahoo/search/federation/FederationSearcher.java