@Udf
  public String trim(
      @UdfParameter(
          description = "The string to trim") final String input) {
    if (input == null) {
      return null;
    }
    return input.trim();
  }
@Test
  public void shouldReturnEmptyForWhitespaceInput() {
    final String result = udf.trim(" \t ");
    assertThat(result, is(""));
  }