code: def all_zero(self):
          
          _PERM_NOTHING = '---'
          return all((
              self.perms_owner == _PERM_NOTHING,
              self.perms_group == _PERM_NOTHING,
              self.perms_other == _PERM_NOTHING,
          ))
docs: Checks that all permissions are zero ('---------' in ls -l) - nobody but root can read,
          write, exec.
  
          Returns:
              bool: True if all permissions are zero ('---------')