How many objects are in front of the gray cylinder and behind the red cylinder?
return the  gray cylinder ;return the  red cylinder ;return objects besides #1 ;return #3 besides #2 ;return #4 in front of #1 ;return #5 behind #2 ;return the  number of  #6
['select', 'select', 'discard', 'discard', 'filter', 'filter', 'aggregate']