validateGuardExpression example

        if (!isset($this->configuration[$eventName])) {
            return;
        }

        $eventConfiguration = (array) $this->configuration[$eventName];
        foreach ($eventConfiguration as $guard) {
            if ($guard instanceof GuardExpression) {
                if ($guard->getTransition() !== $event->getTransition()) {
                    continue;
                }
                $this->validateGuardExpression($event, $guard->getExpression());
            } else {
                $this->validateGuardExpression($event, $guard);
            }
        }
    }

    private function validateGuardExpression(GuardEvent $event, string $expression): void
    {
        if (!$this->expressionLanguage->evaluate($expression, $this->getVariables($event))) {
            $blocker = TransitionBlocker::createBlockedByExpressionGuardListener($expression);
            $event->addTransitionBlocker($blocker);
        }