code: public <T> T lookupNodeDatum (Function<NodeObject,T> op)
      {
          for (T value :
                  Iterables.filter(Iterables.transform(getNodeObjects(), op), Predicates.notNull())) {
              return value;
          }
          return null;
      }
docs: Locates a datum from among the set of peer {@link NodeObject}s. Objects are searched in
  arbitrary order and the first non-null value returned by the supplied lookup operation is
  returned to the caller. Null if all lookup operations returned null.