@Udf
  public <T> List<T> mapValues(final Map<String, T> input) {
    if (input == null) {
      return null;
    }
    return Lists.newArrayList(input.values());
  }
@Test
  public void shouldReturnNullsFromMapWithNulls() {
    final Map<String, Integer> input = Maps.newHashMap();
    input.put("foo", 1);
    input.put(null, null);
    input.put("bar", null);
    List<Integer> result = udf.mapValues(input);
    assertThat(result, containsInAnyOrder(1, null, null));
  }