@Nullable static String lastStringHeader(Headers headers, String key) {
    Header header = headers.lastHeader(key);
    if (header == null || header.value() == null) return null;
    return new String(header.value(), UTF_8);
  }
@Test void lastStringHeader() {
    record.headers().add("b3", new byte[] {'1'});

    assertThat(KafkaHeaders.lastStringHeader(record.headers(), "b3"))
      .isEqualTo("1");
  }