def _iter_chain(self) -> Iterator[SubRequest]:
        """Yield all SubRequests in the chain, from self up.

        Note: does *not* yield the TopRequest.
        """
        current = self
        while isinstance(current, SubRequest):
            yield current
            current = current._parent_request
Yield all SubRequests in the chain, from self up.

        Note: does *not* yield the TopRequest.
        
src/_pytest/fixtures.py