If one person whose face cannot be seen is holding at least one balloon.
return people ;return face of #1 ;return #1 where  #2 can not be seen ;return balloons ;return #4 that #3 are holding ;return number of  #5 for each  #3 ;return #3 where  #6 is at least one ;return number of  #7 ;return if  #8 is equal to  one
['select', 'project', 'filter', 'select', 'filter', 'group', 'comparative', 'aggregate', 'boolean']