@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 shouldReturnNullOnNullValue() {
    assertNull(udf.regexpExtract(null, null));
    assertNull(udf.regexpExtract(null, null, null));
    assertNull(udf.regexpExtract(null, "", 1));
    assertNull(udf.regexpExtract("some string", null, 1));
    assertNull(udf.regexpExtract("some string", "", null));
  }