Determine Player's position around enemy in AI

So I am setting up an Behavior Tree and I would like to have a task that is executed based on the player’s position around the enemy.

Example would be:

Use Tail Whip attack if player is behind enemy

How can I make this happen? I know It would need to be coded inside of a Decorator but beyond that I’m not sure where to go with the code!

Thanks!

You would want to check the players forward vector and if the enemy has the same forward vector ± 10 degrees or something then do your tail whip.