Sets headers needed by proxies: specifically, the Accept and Host
        headers. Only sets headers not provided by the user.

def _set_proxy_headers(self, url, headers=None):
        """
        Sets headers needed by proxies: specifically, the Accept and Host
        headers. Only sets headers not provided by the user.
        """
        headers_ = {'Accept': '*/*'}

        netloc = parse_url(url).netloc
        if netloc:
            headers_['Host'] = netloc

        if headers:
            headers_.update(headers)
        return headers_