code: function getNativeFlags(regex) {
      return hasFlagsProp ?
          regex.flags :
          // Explicitly using `RegExp.prototype.toString` (rather than e.g. `String` or concatenation
          // with an empty string) allows this to continue working predictably when
          // `XRegExp.proptotype.toString` is overridden
          nativ.exec.call(/\/([a-z]*)$/i, RegExp.prototype.toString.call(regex))[1];
  }
docs: Returns native `RegExp` flags used by a regex object.
  
  @private
  @param {RegExp} regex Regex to check.
  @returns {String} Native flags in use.