code: def restore_files(self):
      if self._credentials and ensure_writable_plotly_dir():
          utils.save_json_dict(
              files.CREDENTIALS_FILE, self._credentials
          )
      if self._config and ensure_writable_plotly_dir():
          utils.save_json_dict(files.CONFIG_FILE, self._config)
  
file_path: plotly.py/packages/python/chart-studio/chart_studio/tests/utils.py
imports: import copy
  from unittest import TestCase
  from chart_studio import session, files, utils
  from plotly.files import ensure_writable_plotly_dir
label_desc: Use image node_id 6 for calling the PlotlyTestCase obj's underlying member method code with example usage: obj.restore_files() without return types