What code replaces XXX to make the program output the number $10?$

multiplier $=1$

def do$\_$multiplication$($x$)$:

return x $*$ multiplier

def set$\_$multiplier$($x$)$:

XXX

multiplier $=$ x

user$\_$value $=5$

set$\_$multplier$(2)$

print$($do$\_$multiplication$($user$\_$value$))$