static concat(var_args) {
    let style = '';

    /**
     * @param {!SafeStyle|!Array<!SafeStyle>} argument
     */
    const addArgument = argument => {
      if (Array.isArray(argument)) {
        argument.forEach(addArgument);
      } else {
        style += SafeStyle.unwrap(argument);
      }
    };

    Array.prototype.forEach.call(arguments, addArgument);
    if (!style) {
      return SafeStyle.EMPTY;
    }
    return SafeStyle.createSafeStyleSecurityPrivateDoNotAccessOrElse(style);
  }
Creates a new SafeStyle object by concatenating the values.
@param {...(!SafeStyle|!Array<!SafeStyle>)} var_args
    SafeStyles to concatenate.
@return {!SafeStyle}