code: static byte byteFromBase16String(CharSequence chars, int offset) {
      Utils.checkArgument(chars.length() >= offset + 2, "chars too small");
      return decodeByte(chars.charAt(offset), chars.charAt(offset + 1));
    }
docs: Decodes the specified two character sequence, and returns the resulting {@code byte}.
  
  @param chars the character sequence to be decoded.
  @param offset the starting offset in the {@code CharSequence}.
  @return the resulting {@code byte}
  @throws IllegalArgumentException if the input is not a valid encoded string according to this
  encoding.