static toHex_(x, removeInitialZero = false) {
    const value = x.toString(16).toUpperCase();
    if (removeInitialZero) {
      return value;
    }
    return ('0' + value).slice(-2);
  }
Convert a number to hex
@param {number} x
@param {boolean=} removeInitialZero
@return {string}
@private