private Function<KsqlConfig, Kudf> getUdfFactory(
      final Method method,
      final UdfDescription udfDescriptionAnnotation,
      final String functionName,
      final FunctionInvoker invoker,
      final String sensorName
  ) {
    return ksqlConfig -> {
      final Object actualUdf = FunctionLoaderUtils.instantiateFunctionInstance(
          method.getDeclaringClass(), udfDescriptionAnnotation.name());
      if (actualUdf instanceof Configurable) {
        ExtensionSecurityManager.INSTANCE.pushInUdf();
        try {
          ((Configurable) actualUdf)
              .configure(ksqlConfig.getKsqlFunctionsConfigProps(functionName));
        } finally {
          ExtensionSecurityManager.INSTANCE.popOutUdf();
        }
      }
      final PluggableUdf theUdf = new PluggableUdf(invoker, actualUdf);
      return metrics.<Kudf>map(m -> new UdfMetricProducer(
          m.getSensor(sensorName),
          theUdf,
          Time.SYSTEM
      )).orElse(theUdf);
    };
  }
@Test
  public void shouldLoadFunctionWithListReturnType() {
    // Given:
    final UdfFactory toList = FUNC_REG.getUdfFactory(FunctionName.of("tolist"));

    // When:
    final List<SqlArgument> args = Collections.singletonList(SqlArgument.of(SqlTypes.STRING));
    final KsqlScalarFunction function
        = toList.getFunction(args);

    assertThat(function.getReturnType(args),
        is(SqlTypes.array(SqlTypes.STRING))
    );
  }