public function setAdapter($adapter)
    {
        if ($adapter instanceof Zend_Filter_Compress_CompressInterface) {
            $this->_adapter = $adapter;
            return $this;
        }
        if (!is_string($adapter)) {

            throw new Zend_Filter_Exception('Invalid adapter provided; must be string or instance of Zend_Filter_Compress_CompressInterface');
        }
        $this->_adapter = $adapter;

        return $this;
    }