private ComponentSpecification asSourceSpec(String source) {
        try {
            return new ComponentSpecification(source);
        } catch (Exception e) {
            throw new IllegalInputException("The source ref '" + source + "' used for federation is not valid.", e);
        }
    }
TODO This is probably a dirty hack for bug 4711376. There are probably better ways.
But I will leave that to trd-processing@

@param group the merging hitgroup to be updated if necessary
@param orderer the per provider hit orderer
@return he hitorderer chosen
container-search/src/main/java/com/yahoo/search/federation/FederationSearcher.java