A list of the top 5 countries by number of invoices. List country name and number of invoices.
return countries ;return invoices  of   #1 ;return number of  #2 for each #1 ;return the  top 5 highest of   #3 ;return #1 where #3 is equal to any of   #4 ;return names of   #5 ;return #6 ,  #4
['select', 'project', 'group', 'aggregate', 'comparative', 'project', 'union']