def lookup(self, allowed_types, **kwargs):
        """Lookup an object of type (allowed_types).  kwargs is sent
        directly to the catalog.
        """
        at = getToolByName(self, 'archetype_tool')
        for portal_type in allowed_types:
            catalog = at.catalog_map.get(portal_type, [None])[0]
            catalog = getToolByName(self, catalog)
            kwargs['portal_type'] = portal_type
            brains = catalog(**kwargs)
            if brains:
                return brains
Lookup an object of type (allowed_types).  kwargs is sent
        directly to the catalog.