code: def extend(self):
          
          graph = GraphAPI()
  
          response = graph.get('oauth/access_token',
              client_id = FACEBOOK_APPLICATION_ID,
              client_secret = FACEBOOK_APPLICATION_SECRET_KEY,
              grant_type = 'fb_exchange_token',
              fb_exchange_token = self.token
          )
  
          components = parse_qs(response)
  
          self.token = components['access_token'][0]
          self.expires_at = now() + timedelta(seconds = int(components['expires'][0]))
  
          self.save()
docs: Extend the OAuth token.