public TensorType defaultTypeOf(Reference reference) {
        if ( ! FeatureNames.isSimpleFeature(reference))
            throw new IllegalArgumentException("This can only be called for simple references, not " + reference);
        if (reference.name().equals("query")) { // we do not require all query features to be declared, only non-doubles
            queryFeaturesNotDeclared.add(reference);
            return TensorType.empty;
        }
        return null;
    }
Returns the default type for this simple feature, or null if it does not have a default
config-model/src/main/java/com/yahoo/schema/MapEvaluationTypeContext.java