If one of the pelicans has a fish in its mouth.
return pelicans ;return fish ;return mouth of #1 ;return #3 that has #2 in  ;return #1 that has #4 ;return number of  #5 ;return if  #6 is equal to  one
['select', 'select', 'project', 'filter', 'filter', 'aggregate', 'boolean']