code: def get_extended_access_token(access_token, application_id, application_secret_key, api_version=None):
      
      graph = GraphAPI(version=api_version)
  
      response = graph.get(
          path='oauth/access_token',
          client_id=application_id,
          client_secret=application_secret_key,
          grant_type='fb_exchange_token',
          fb_exchange_token=access_token
      )
  
      try:
          components = parse_qs(response)
      except AttributeError:  # api_version >= 2.3 returns a dict
          return response['access_token'], None
  
      token = components['access_token'][0]
  
      try:
          expires_at = datetime.now() + timedelta(seconds=int(components['expires'][0]))
      except KeyError:  # there is no expiration
          expires_at = None
  
      return token, expires_at
docs: Get an extended OAuth access token.
  
      :param access_token: A string describing an OAuth access token.
      :param application_id: An integer describing the Facebook application's ID.
      :param application_secret_key: A string describing the Facebook application's secret key.
  
      Returns a tuple with a string describing the extended access token and a datetime instance
      describing when it expires.