def __delitem__(self, flavor):
        # XXX: We really should be testing for a deps.deps.Flavor
        # instance, but the split of Flavor from DependencySet would
        # cause too much code breakage right now....
        assert(isinstance(flavor, deps.deps.DependencySet))
        if flavor.isEmpty():
            return
        idtable.IdTable.__delitem__(self, flavor.freeze())