isImmuneToFire() causes error

Hello, I'm trying to make my block and armor items immune to fire/lava just by editing the code and I get an error every time I try and force it to do so: https://imgur.com/a/N0uCN0a

Is there a way to make item blocks and armor immune to fire? The equipped armor already has the ability to make the player fire resistant, but not the items themselves.