Как проверить идет ли трафик через прокси?

class SOCKS_IMAP4(imaplib.IMAP4):
    def __init__(self, host = '', port = imaplib.IMAP4_PORT,proxy_type = None, proxy = None):
            self.proxy = proxy
            self.proxy_type = proxy_type
            imaplib.IMAP4.__init__(self, host, port)
    def open(self,host,port=imaplib.IMAP4_PORT):
        self.host = host
        self.port = port        
        if self.proxy and self.proxy_type:
            proxy_ip,proxy_port = self.proxy.split(':')
            self.sock = socksocket()
            self.sock.setproxy(self.proxy_type,proxy_ip,int(proxy_port))
        self.sock.connect((host,port))
        self.file = self.sock.makefile('rb')