def get_slot_position_for(self, instance):
        """Returns the slot where the instance passed in is located. If not
        found, returns None
        """
        uid = api.get_uid(instance)
        slot = filter(lambda s: s['analysis_uid'] == uid, self.getLayout())
        if not slot:
            return None
        return to_int(slot[0]['position'])
Returns the slot where the instance passed in is located. If not
        found, returns None