/** -------------------------
  * Get the repeated driving assertion plan id for one driver and one shift
  *
  * @param Driver $driver
  * @param Shift $shift
  * @return mixed|null
  */
 protected function getPlanIdFor(Driver $driver, Shift $shift)
 {
     $drivingAssertions = $driver->getDrivingAssertions();
     /** @var DrivingAssertion $drivingAssertion */
     foreach ($drivingAssertions as $drivingAssertion) {
         if ($drivingAssertion->getShift() === $shift) {
             /** @var RepeatedDrivingAssertionPlan $rdaPlan */
             $rdaPlan = $drivingAssertion->getRepeatedDrivingAssertionPlan();
             return is_object($rdaPlan) ? $rdaPlan->getId() : null;
         }
     }
     return null;
 }