private FederationResult search(Query query, Execution execution, Collection<Target> targets) {
        FederationResult.Builder result = new FederationResult.Builder();
        for (Target target : targets)
            result.add(target, searchAsynchronously(query, execution, Window.from(targets, query), target));
        return result.build();
    }
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