docs: def parent(self):
          "Get this object's parent"
          if self._parent:
              return self._parent
          # auto-compute parent if needed
          elif getattr(self, '__parent_type__', None):
              return self._get_subfolder('..' if self._url[2].endswith('/')
                                              else '.', self.__parent_type__)
          else:
              raise AttributeError("%r has no parent attribute" % type(self))