If there are two babies with balloons at or on their head.
return babies ;return balloons ;return head of #1 ;return #1 where  #2 is at #3 ;return #1 where  #2 is on #3 ;return #4 , #5 ;return number of  #6 ;return if  #7 is equal to  two
['select', 'select', 'project', 'comparative', 'comparative', 'union', 'aggregate', 'boolean']