@Override
    @Deprecated
    public <VR> KStream<K, VR> flatTransformValues(final org.apache.kafka.streams.kstream.ValueTransformerSupplier<? super V, Iterable<VR>> valueTransformerSupplier,
                                                   final String... stateStoreNames) {
        Objects.requireNonNull(valueTransformerSupplier, "valueTransformerSupplier can't be null");
        return doFlatTransformValues(
            toValueTransformerWithKeySupplier(valueTransformerSupplier),
            NamedInternal.empty(),
            stateStoreNames);
    }
@Test
    @SuppressWarnings("deprecation")
    public void shouldNotAllowNullValueTransformerSupplierOnFlatTransformValues() {
        final NullPointerException exception = assertThrows(
            NullPointerException.class,
            () -> testStream.flatTransformValues((org.apache.kafka.streams.kstream.ValueTransformerSupplier<Object, Iterable<Object>>) null));
        assertThat(exception.getMessage(), equalTo("valueTransformerSupplier can't be null"));
    }