If there are exactly six musicians playing instruments, three in each image.
return musicians ;return instruments ;return #1 playing #2 ;return images of #3 ;return number of  #3 for each  #4 ;return #4 where  #5 is equal to  three ;return number of  #6 ;return if  #7 is equal to  two
['select', 'select', 'filter', 'project', 'group', 'comparative', 'aggregate', 'boolean']