docs: def get_default_bios_settings(self, only_allowed_settings=True):
          """Get default BIOS settings.
  
          :param: only_allowed_settings: True when only allowed BIOS settings
                  are to be returned. If False, All the BIOS settings supported
                  by iLO are returned.
          :return: a dictionary of default BIOS settings(factory settings).
                   Depending on the 'only_allowed_settings', either only the
                   allowed settings are returned or all the supported settings
                   are returned.
          :raises: IloError, on an error from iLO.
          :raises: IloCommandNotSupportedError, if the command is not supported
                   on the server.
          """
          headers_bios, bios_uri, bios_settings = self._check_bios_resource()
          # Get the BaseConfig resource.
          try:
              base_config_uri = bios_settings['links']['BaseConfigs']['href']
          except KeyError:
              msg = ("BaseConfigs resource not found. Couldn't apply the BIOS "
                     "Settings.")
              raise exception.IloCommandNotSupportedError(msg)
  
          status, headers, config = self._rest_get(base_config_uri)
          if status != 200:
              msg = self._get_extended_error(config)
              raise exception.IloError(msg)
  
          for cfg in config['BaseConfigs']:
              default_settings = cfg.get('default')
              if default_settings:
                  break
          else:
              msg = ("Default BIOS Settings not found in 'BaseConfigs' "
                     "resource.")
              raise exception.IloCommandNotSupportedError(msg)
  
          if only_allowed_settings:
              return utils.apply_bios_properties_filter(
                  default_settings, constants.SUPPORTED_BIOS_PROPERTIES)
          return default_settings