code: def currentdir(self) -> str:
          if self._currentdir is None:
              directories = self.availabledirs.folders
              if len(directories) == 1:
                  self.currentdir = directories[0]
              elif self.DEFAULTDIR in directories:
                  self.currentdir = self.DEFAULTDIR
              else:
                  prefix = (f'The current working directory of the '
                            f'{objecttools.classname(self)} object '
                            f'has not been defined manually and cannot '
                            f'be determined automatically:')
                  if not directories:
                      raise RuntimeError(
                          f'{prefix} `{objecttools.repr_(self.basepath)}` '
                          f'does not contain any available directories.')
                  if self.DEFAULTDIR is None:
                      raise RuntimeError(
                          f'{prefix} `{objecttools.repr_(self.basepath)}` '
                          f'does contain multiple available directories '
                          f'({objecttools.enumeration(directories)}).')
                  raise RuntimeError(
                      f'{prefix} The default directory ({self.DEFAULTDIR}) '
                      f'is not among the available directories '
                      f'({objecttools.enumeration(directories)}).')
          return self._currentdir