private static Pair<String,Boolean> javaSuperType(NewDocumentType docType) {
        String ret = "com.yahoo.document.Document";
        Collection<NewDocumentType> specInheriteds = specificInheriteds(docType);
        boolean singleExtends = singleInheritance(specInheriteds);
        if (!specInheriteds.isEmpty() && singleExtends) ret = className(specInheriteds.iterator().next().getName());
        return new Pair<>(ret, !singleExtends);
    }
The Java class the class of the given type should inherit from. If the input type inherits from _one_
other type, use that, otherwise Document.
vespa-documentgen-plugin/src/main/java/com/yahoo/vespa/DocumentGenMojo.java