@Udf
  public <T> Integer calcArrayLength(
      @UdfParameter(description = "The array") final List<T> array
  ) {
    if (array == null) {
      return null;
    }
    return array.size();
  }
@Test
  public void shouldReturnNullForNullArray() {
    assertThat(udf.calcArrayLength(null), is(nullValue()));
  }