docs: def _get_from_cache(self, expr):
          """Obtain cached result, prepend with the keyname if necessary, and
          indent for the current level"""
          is_cached, res = super()._get_from_cache(expr)
          if is_cached:
              indent_str = "    " * self._print_level
              return True, indent(res, indent_str)
          else:
              return False,  None