Return the ids of the two department store chains with the most department stores.
SELECT dept_store_chain_id FROM department_stores GROUP BY dept_store_chain_id ORDER BY count(*) DESC LIMIT 2
SELECT dept_store_chain_id FROM department_stores GROUP BY dept_store_chain_id ORDER BY count(*) DESC LIMIT 2
[{'dept_store_chain_id': 4}, {'dept_store_chain_id': 3}]