what if there are preconditions

Preconditions:

row and col$$ len$($grid$)$

$-0$ len$($grid$)$

$-$ len$($grid$[$i$])==$ len$($grid$)$

for each value of i in range$($len$($grid$))$

$>>>$ grid$\_$one $=[[\text{'}$a$\text{'},$ UNKNOWN$],[$UNKNOWN$,\text{'}$b$\text{'}]]$

$>>>$ is$\_$not$\_$given$\_$char$(1,1,$ grid$\_$one, UNKNOWN$)$

True

$>>>$ is$\_$not$\_$given$\_$char$(0,1,$ grid$\_$one, UNKNOWN$)$

False

$"""$