human
Solve the following python programming problem given the following code:
def ListClientLogs(client, obj_store, auth_credentials, request, callback) : 
    'Returns a list of client logs matching the specified client user
  id and start/end timestamps date range.
  ' 
    def _OnListClientLogs(log_urls) : 
        logging.info (('LIST CLIENT LOGS: admin: %s, client user_id: %d, start: %s, end: %s, filter: %s, num_logs: %d' % (auth_credentials, request ['user_id'], ClientLog._IsoDate (request ['start_timestamp']), ClientLog._IsoDate (request ['end_timestamp']), request.get ('filter', None), len (log_urls)))) 
        response = { 
            'log_urls' : log_urls, 
} 
        callback (response) 
ClientLog.ListClientLogs (request ['user_id'], request ['start_timestamp'], request ['end_timestamp'], request.get ('filter', None), <MASK>) 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def _OnListClientLogs(