code: def is_none_or(self):
          
          if self._subject is None:
              return NoOpInspector(subject=self._subject, error_factory=self._error_factory)
          else:
              return self
docs: Ensures :attr:`subject` is either ``None``, or satisfies subsequent (chained) conditions::
  
              Ensure(None).is_none_or.is_an(int)