public function isValidEvent(ilCalendarEntry $a_event)
 {
     global $ilUser;
     $booking = new ilBookingEntry($a_event->getContextId());
     // portfolio embedded: filter by consultation hour groups?
     if (!is_array($this->group_ids) || in_array($booking->getBookingGroup(), $this->group_ids)) {
         // do not filter against course/group in portfolio
         if ($this->cats->getMode() == ilCalendarCategories::MODE_PORTFOLIO_CONSULTATION) {
             $booking->setTargetObjIds(null);
         }
         if (($this->user_id == $ilUser->getId() || !$booking->isBookedOut($a_event->getEntryId(), true)) && $booking->isTargetObjectVisible($this->cats->getTargetRefId())) {
             return true;
         }
     }
     return false;
 }