code: function isPlatformModifierKeyOnly(event) {
    return !event.altKey &&
      (olHas.MAC ? event.metaKey : event.ctrlKey) &&
      !event.shiftKey;
  }
docs: Same as `ol.events.condition.platformModifierKeyOnly`.
  @param {JQueryEventObject} event Event.
  @return {boolean} True if only the platform modifier key is pressed.
  @private