code: public Collection<?> saveObjCollection(Keyspace keyspace, Collection<?> objColl) {
      Mutator<byte[]> m = HFactory.createMutator(keyspace, BytesArraySerializer.get());
      Collection<?> retColl = saveObjCollection(keyspace, objColl, m);
      m.execute();
      return retColl;
    }
docs: Persists the object collection using a single batch mutate. It is up to the
  client to partition large collections appropriately so not to cause timeout
  or buffer overflow issues. The objects can be heterogenous (mapping to
  multiple column families, etc.)
  
  @param keyspace
  @param objColl
  @return