If a forward-headed dog is staying afloat by means of some item that floats.
return dog ;return #1 that is forward-headed ;return item ;return #3 that floats ;return #2 that is staying afloat ;return #5 that is by means of #4 ;return number of  #6 ;return if  #7 is at least one
['select', 'filter', 'select', 'filter', 'filter', 'filter', 'aggregate', 'boolean']