code: def _update_from_file(self, filename):
          
          if os.path.exists(filename):
              try:
                  with open(filename, 'r') as config_file:
                      yaml_dict = yaml.safe_load(config_file.read())
                      if yaml_dict is not None:
                          self._update_dict(self._config, yaml_dict)
              except IsADirectoryError:
                  raise ConfigLoadError(
                      'The specified configuration file is a directory not a file')
          else:
              raise ConfigLoadError('The config file {} does not exist'.format(filename))
docs: Helper method to update an existing configuration with the values from a file.
  
          Loads a configuration file and replaces all values in the existing configuration
          dictionary with the values from the file.
  
          Args:
              filename (str): The path and name to the configuration file.