question: If each image contains exactly one flute and nothing else, displayed diagonally.
#1 return flutes 
#2 return #1 that are displayed diagonally 
#3 return images 
#4 return number of  #2 for each  #3 
#5 return #3 where  #4 is equal to  one 
#6 return number of  #3 
#7 return number of  #5 
#8 return if  #6 is equal to  #7 
#9 return #3 that contains nothing besides  #2 
#10 return number of  #9 
#11 return if  #6 is equal to  #10 
#12 return if  both  #8 and #11 are true