protected function getFieldsetHelper()
    {
    	if ($this->fieldsetHelper) {
    	    return $this->fieldsetHelper;
    	}

    	if (method_exists($this->view, 'plugin')) {
    	    $this->fieldsetHelper = $this->view->plugin($this->defaultFieldsetHelper);
    	}

    	if (!$this->fieldsetHelper instanceof AbstractHelper) {
    	    // @todo Ideally the helper should implement an interface.
    	    throw InvalidHelperException::invalidHelperInstance($this->fieldsetHelper);
    	}

    	return $this->fieldsetHelper;
    }