code: def _update_defaults(self, defaults):
          
  
          # Accumulate complex default state.
          self.values = optparse.Values(self.defaults)
          late_eval = set()
          # Then set the options with those values
          for key, val in self._get_ordered_configuration_items():
              # '--' because configuration supports only long names
              option = self.get_option('--' + key)
  
              # Ignore options not present in this parser. E.g. non-globals put
              # in [global] by users that want them to apply to all applicable
              # commands.
              if option is None:
                  continue
  
              if option.action in ('store_true', 'store_false', 'count'):
                  try:
                      val = strtobool(val)
                  except ValueError:
                      error_msg = invalid_config_error_message(
                          option.action, key, val
                      )
                      self.error(error_msg)
  
              elif option.action == 'append':
                  val = val.split()
                  val = [self.check_default(option, key, v) for v in val]
              elif option.action == 'callback':
                  late_eval.add(option.dest)
                  opt_str = option.get_opt_string()
                  val = option.convert_value(opt_str, val)
                  # From take_action
                  args = option.callback_args or ()
                  kwargs = option.callback_kwargs or {}
                  option.callback(option, opt_str, val, self, *args, **kwargs)
              else:
                  val = self.check_default(option, key, val)
  
              defaults[option.dest] = val
  
          for key in late_eval:
              defaults[key] = getattr(self.values, key)
          self.values = None
          return defaults
docs: Updates the given defaults with values from the config files and
          the environ. Does a little special handling for certain types of
          options (lists).