code: def test_set_credentials(self):
      expected_auth = None
      self.assertEqual(self.rnw.auth, expected_auth)
  
      username, password = "username", "password"
      expected_auth = HTTPBasicAuth(username, password)
      self.rnw.set_credentials(username, password)
      self.assertEqual(self.rnw.auth, expected_auth)
  
imports: import json
  import requests
  from requests.auth import HTTPBasicAuth
  from tabpy.tabpy_tools.rest import RequestsNetworkWrapper, ServiceClient
  import unittest
  from unittest.mock import Mock
label_desc: Use image node_id 17 for calling the TestRequestsNetworkWrapper obj's underlying member method code with example usage: obj.test_set_credentials() without return types