Is the gray ball the same material as the small blue one?
return balls ;return #1 that  are gray ;return the   material of #2 ;return #1 that  are small ;return #4 that  are blue ;return the   material of #5 ;return if  #3 is  the   same as #6
['select', 'filter', 'project', 'filter', 'filter', 'project', 'boolean']