what is the loop invariant for the following function:

def is$\_$prime $($n$)$ :

pre: n is natural $>=2$ ;

post: true if n is prime, false otherwise

m $=2$;

result $=$ true;

while m $<=$ n$/2\{$

if n$\%$m $==0\{$

result $=$ false;

$\}$

m $=$ m$+1$;

$\}$

return result