docs: private static byte[] idInBytes(final short idwidth, final long lid) {
      if (idwidth <= 0) {
        throw new AssertionError("negative idwidth: " + idwidth);
      }
      final byte[] id = Bytes.fromLong(lid);
      for (int i = 0; i < id.length - idwidth; i++) {
        if (id[i] != 0) {
          System.err.println(lid + " is too large to fit on " + idwidth
              + " bytes.  Maybe you forgot to adjust --idwidth?");
          return null;
        }
      }
      return Arrays.copyOfRange(id, id.length - idwidth, id.length);
    }