Respect\Validation\Rules\AbstractRelated::assert PHP Method

    public function assert($input)
    {
        $hasReference = $this->hasReference($input);
        if ($this->mandatory && !$hasReference) {
            throw $this->reportError($input, ['hasReference' => false]);
        }
        try {
            return $this->decision('assert', $hasReference, $input);
        } catch (ValidationException $e) {
            throw $this->reportError($this->reference, ['hasReference' => true])->addRelated($e);
        }
    }