code: public <T> T queryColumns(K key, HSlicePredicate<N> predicate,
        ColumnFamilyRowMapper<K, N, T> mapper) {
      return doExecuteSlice(key, predicate, mapper);
    }
docs: Queries a range of columns at the given key and maps them to an object of
  type OBJ using the given mapping object
  
  @param <T>
  @param key
  @param predicate The {@link HSlicePredicate} which can hold specific column names
  or a range of columns
  @param mapper
  @return