@Override
  public byte[] serialize(final String topic, final List<?> values) {
    if (values == null) {
      return null;
    }

    final T single = extractOnlyColumn(values, topic);
    return inner.serialize(topic, single);
  }
@Test
  public void shouldThrowIfMoreThanOneValue() {
    // When:
    final Exception e = assertThrows(
        SerializationException.class,
        () -> serializer.serialize("t", ImmutableList.of("too", "many"))
    );

    // Then:
    assertThat(e.getMessage(), is("Column count mismatch on serialization. topic: t, expected: 1, got: 2"));
  }