if query and query.get('collections'):
            # Find acquisition ids in this collection, add to query
            collection_id = query.pop('collections')
            a_ids = AcquisitionStorage().get_all_el({'collections': bson.ObjectId(collection_id)}, None, {'session': 1})
            query['_id'] = {'$in': list(set([a['session'] for a in a_ids]))}