def purge(obj, selector, comment='', metadata={}, countPurged=True):
    """Purge a Version of a Content

        Purge the given version of the object. Referenced content objects
        versions aren't purged. No recursive purging takes place.

        Also counts purged versions if ``True`` is passed to ``countPurged``
        (see interface documentation for details).

        Example:

        An object got saved ten times. Two versions got purged in earlier
        calls. The histor looks like this (a ``p`` stands for purged)::

            versions: 0, 1, 2, 3p, 4p, 5, 6, 7, 8, 9
            selector: 0, 1, 2, 3,  4,  5, 6, 7, 8, 9 (countPurged==True)
            selector: 0, 1, 2, -,  -,  3, 4, 5, 6, 7 (countPurged==False)

        The comment and metadata passed may be used to store informations
        about the reasons of the purging.
        """
