human
Solve the following python programming problem given the following code:
def __call__(self, environ, start_response) : 
    env_identity = self._keystone_identity (environ) 
    if (self.allow_overrides and environ.get ('swift.authorize_override', False)) : 
        msg = 'Authorizing from an overriding middleware' 
        self.logger.debug (msg) 
        return self.app (environ, keystone_start_response) 
if env_identity : 
        self.logger.debug ('Using identity: %r', env_identity) 
        environ ['REMOTE_USER'] = env_identity.get ('tenant') 
        environ ['keystone.identity'] = env_identity 
        environ ['swift.authorize'] = functools.partial (self.authorize, env_identity) 
        user_roles = (r.lower () for r in env_identity.get ('roles', [])) 
        if (self.reseller_admin_role in user_roles) : 
            environ ['reseller_request'] = True 
else : 
        self.logger.debug ('Authorizing as anonymous') 
        environ ['swift.authorize'] = self.authorize_anonymous 
environ ['swift.clean_acl'] = swift_acl.clean_acl 
    def keystone_start_response(status, response_headers, exc_info = None) : 
        project_domain_id = None 
        for (key, val) in response_headers : 
            if (key.lower () == PROJECT_DOMAIN_ID_SYSMETA_HEADER) : 
                project_domain_id = val 
                break 
if project_domain_id : 
            response_headers.append ((PROJECT_DOMAIN_ID_HEADER, project_domain_id)) 
return start_response (status, response_headers, exc_info) 
return self.app (environ, keystone_start_response) 

    
    

    Fix the buggy line: return self.app (environ, keystone_start_response)
assistant
#Here is Python code to fix the buggy line: return self.

return self.app (environ, start_response)