    def _ensureSnapshotsFolder(self, subdir=None):
        """ Ensure that the appropriate snapshot folder exists.
        """
        path = ['snapshots', self._snapshot_id]

        if subdir is not None:
            path.extend(subdir.split('/'))

        current = self._tool

        for element in path:

            if element not in current.objectIds():
                # No Unicode IDs!
                current._setObject(str(element), Folder(element))

            current = current._getOb(element)

        return current