@Udf(description = "Returns first substring of the input that matches the given regex pattern")
  public String regexpExtract(
      @UdfParameter(description = "The regex pattern") final String pattern,
      @UdfParameter(description = "The input string to apply regex on") final String input
  ) {
    return regexpExtract(pattern, input, 0);
  }
@Test
  public void shouldReturnNullWhenNoMatch() {
    assertNull(udf.regexpExtract("tst", "test string"));
  }