'Returns a urllib3 connection for the given URL. This should not be
called from user code, and is only exposed for use when subclassing the
:class:`HTTPAdapter <requests.adapters.HTTPAdapter>`.
:param url: The URL to connect to.
:param proxies: (optional) A Requests-style dictionary of proxies used on this request.'

def get_connection(self, url, proxies=None):

    proxies = (proxies or {})
    proxy = proxies.get(urlparse(url.lower()).scheme)
    if proxy:
        proxy = prepend_scheme_if_needed(proxy, 'http')
        proxy_manager = self.proxy_manager_for(proxy)
        conn = proxy_manager.connection_from_url(url)
    else:
        parsed = urlparse(url)
        url = parsed.geturl()
        conn = self.poolmanager.connection_from_url(url)
    return conn
