code: public static boolean isIndex(Nanopub np) {
  		for (Statement st : np.getPubinfo()) {
  			if (!st.getSubject().equals(np.getUri())) continue;
  			if (!st.getPredicate().equals(RDF.TYPE)) continue;
  			if (!st.getObject().equals(NanopubIndex.NANOPUB_INDEX_URI)) continue;
  			return true;
  		}
  		return false;
  	}
docs: no instances allowed