'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):

    headers_ = {'Accept': '*/*'}
    netloc = parse_url(url).netloc
    if netloc:
        headers_['Host'] = netloc
    if headers:
        headers_.update(headers)
    return headers_
