@Nullable
  public static TraceContextOrSamplingFlags parseB3SingleFormat(CharSequence b3) {
    return parseB3SingleFormat(b3, 0, b3.length());
  }
@Test void parseB3SingleFormat_padded() {
    assertThat(
      parseB3SingleFormat("0000000000000000" + traceId + "-" + spanId + "-1-" + parentId).context()
    ).isEqualToComparingFieldByField(TraceContext.newBuilder()
      .traceId(Long.parseUnsignedLong(traceId, 16))
      .parentId(Long.parseUnsignedLong(parentId, 16))
      .spanId(Long.parseUnsignedLong(spanId, 16))
      .sampled(true).build()
    );
  }