public function performHttpRequest($method, $url, $headers = array(), $body = null, $contentType = null, $remainingRedirects = null)
    {
        if ($this->_httpClient instanceof Zend_Gdata_HttpClient) {
            $filterResult = $this->_httpClient->filterHttpRequest($method, $url, $headers, $body, $contentType);
            $method = $filterResult['method'];
            $url = $filterResult['url'];
            $body = $filterResult['body'];
            $headers = $filterResult['headers'];
            $contentType = $filterResult['contentType'];
            return $this->_httpClient->filterHttpResponse(parent::performHttpRequest($method, $url, $headers, $body, $contentType, $remainingRedirects));
        } else {
            return parent::performHttpRequest($method, $url, $headers, $body, $contentType, $remainingRedirects);
        }
    }