public function addThumbnailRule(ThumbnailRuleInterface $thumbnailRule)
	{
	    if ($thumbnailRule instanceof ImagineAwareInterface) {
	        // not very LSP but handy
	        if (!$thumbnailRule->getImagine()) {
	           $thumbnailRule->setImagine($this->getImagine(), $this->getImagineOptions());
	        }
	    }
	    $this->thumbnailRules[] = $thumbnailRule;
	}