Where is the optimal place to insert a print statement in the for loop of the following code to see how the list is being built and help debug the code?

$1$ multiples $=[]$

$2$

$3$ for threeD in range$(1,3)$:

$4$

$5$ multiples.append$([])$

$6$

$7$ for twoD in range$(1,3)$:

$8$

$9$ multiples$[$threeD$-1].$append$([])$

$10$

$11$ for oneD in range$(1,3)$:

$12$

$13$ multiples$[$threeD$-1][$twoD$-1].$append$($oneD$)$

$14$

line $14$

line $6$

line $10$

line $4$