Show the customer id and number of accounts with most accounts.
return customers ;return accounts  of #1 ;return number of #2 for each #1 ;return #1 where #3 is  highest ;return customer id of #4 ;return accounts  of #4 ;return number of #6 ;return #5 , #7
['select', 'project', 'group', 'superlative', 'project', 'project', 'aggregate', 'union']