@Udf
  public String extractProtocol(
      @UdfParameter(description = "a valid URL to extract a protocl from") final String input) {
    return UrlParser.extract(input, URI::getScheme);
  }
@Test
  public void shouldReturnNullIfNoProtocol() {
    assertThat(
            extractUdf.extractProtocol("///current/ksql/docs/syntax-reference.html#scalar-functions"),
            nullValue());
  }