Modify the binary search function from below so that, instead of returning $-1$ when the target value is not in the list, raises a TargetNotFound exception $($you$\text{'}$ll need to define this exception class$).$ Otherwise it should function normally. Name this function bin$\_$except.

def binary$\_$search$($a$\_$list, target$)$:

$"""$

Searches a$\_$list for an occurrence of target

If found, returns the index of its position in the list

If not found, returns $-1,$ indicating the target value isn't in the list

$"""$

first $=0$

last $=$ len$($a$\_$list$)-1$

while first $<=$ last:

middle $=($first $+$ last$)//2$

if a$\_$list$[$middle$]==$ target:

return middle

if a$\_$list$[$middle$]>$ target:

last $=$ middle $-1$

else:

first $=$ middle $+1$

return $-1$

The file must be named: bin$\_$except.py