@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 shouldReturnSubstringWhenMatched() {
    assertEquals(udf.regexpExtract("e.*", "test string"), "est string");
    assertEquals(udf.regexpExtract(".", "test string"), "t");
    assertEquals(udf.regexpExtract("[AEIOU].{4}", "usEr nAme 1"), "Er nA");
  }