docs: public CodeType getType(final Bits bits) {
      if (null != this.bitDepth) {
        if (bits.bitLength == this.bitDepth) {
          return CodeType.Terminal;
        }
        if (bits.bitLength < this.bitDepth) {
          return CodeType.Prefix;
        }
        throw new IllegalArgumentException();
      }
      return CodeType.Unknown;
    }