human
Solve the following python programming problem given the following code:
def __call__(self, environ, start_response) : 
    cookies = request.get_cookies (environ) 
    if (self.cookie_name in cookies) : 
        cookie_value = cookies [self.cookie_name].value 
else : 
        cookie_value = '' 
if cookie_value : 
        if self.include_ip : 
            remote_addr = environ ['REMOTE_ADDR'] 
else : 
            remote_addr = '0.0.0.0' 
try : 
            (timestamp, userid, tokens, user_data) = parse_ticket (self.secret, cookie_value, remote_addr, self.digest_algo) 
            tokens = ','.join (tokens) 
            environ ['REMOTE_USER'] = userid 
            if environ.get ('REMOTE_USER_TOKENS') : 
                tokens = ((environ ['REMOTE_USER_TOKENS'] + ',') + self) 
environ ['REMOTE_USER_TOKENS'] = tokens 
            environ ['REMOTE_USER_DATA'] = user_data 
            environ ['AUTH_TYPE'] = 'cookie' 
except BadTicket : 
            pass 
set_cookies = [] 
    def set_user(userid, tokens = '', user_data = '') : 
        set_cookies.extend (self.set_user_cookie (environ, userid, tokens, user_data)) 
def logout_user() : 
        set_cookies.extend (self.logout_user_cookie (environ)) 
environ ['paste.auth_tkt.set_user'] = set_user 
    environ ['paste.auth_tkt.logout_user'] = logout_user 
    if (self.logout_path and (environ.get ('PATH_INFO') == self.logout_path)) : 
        logout_user () 
def cookie_setting_start_response(status, headers, exc_info = None) : 
        headers.extend (set_cookies) 
        return start_response (status, headers, exc_info) 
return self.app (environ, cookie_setting_start_response) 

    
    

    Fix the buggy line: tokens = ((environ ['REMOTE_USER_TOKENS'] + ',') + self)
assistant
#Here is Python program to fix the buggy line: tokens = ((environ ['REMOTE_USER_TOKENS'] + ',') + self)
.

tokens = ((environ ['REMOTE_USER_TOKENS'] + ',') + tokens)