code: def test_use_credentials():
      conf.clear()
      with use_credentials(None):
          assert len(conf) == 0
  
      s3_creds = {
          "s3": {
              "client_kwargs": {
                  "endpoint_url": "http://localhost:9000",
                  "aws_access_key_id": "test",
                  "aws_secret_access_key": "test",
              }
          }
      }
      with use_credentials(s3_creds):
          assert len(conf) == 1
          assert conf == s3_creds
  
      assert len(conf) == 0
  
imports: import functools
  import json
  import logging
  import numpy
  import pandas
  import pytest
  from fsspec.config import conf
  from ludwig.api import LudwigModel
  from ludwig.data.cache.types import CacheableDataframe
  from ludwig.data.dataset_synthesizer import build_synthetic_dataset_df
  from ludwig.utils.data_utils import add_sequence_feature_column, figure_data_format_dataset, get_abs_path, hash_dict, NumpyEncoder, PANDAS_DF, read_csv, read_html, read_parquet, sanitize_column_names, use_credentials
  from tests.integration_tests.utils import private_param
label_desc: Use image node_id 6 for calling a global function with example usage: test_use_credentials() without return types