public static FeatureMap deserialize(FeatureDomainProto proto) {
        return ProtoUtil.deserialize(proto);
    }
@Test
    public void testSerialization() {
        FeatureMap fm = buildMap();
        FeatureDomainProto fmProto = fm.serialize();
        FeatureMap deserFm = FeatureMap.deserialize(fmProto);
        assertEquals(fm, deserFm);

        ImmutableFeatureMap ifm = new ImmutableFeatureMap(fm);
        FeatureDomainProto ifmProto = ifm.serialize();
        FeatureMap deserIfm = FeatureMap.deserialize(ifmProto);
        assertEquals(ifm, deserIfm);
    }