code: def _retrieve(self, config_file=None):
          
          with open(config_file or _DEFAULT_PATH, 'r') as f:
              creds = json.load(f)
          self._key = creds.get('key')
          self._base_url = creds.get('base_url')
          self._username = creds.get('username')
docs: Retrives credentials from a file. Defaults to the user config
          directory