Actually I did not try to find from where it's called.
Thread is about medikit, so all you have to do is to search a class which is similar to what you search. Here you find easily CTFMedikit in the list and you have all the relations functions:
From that, OP wants to do something when you heal, usually you would look for PrimaryAttack, but here the only function which makes sense is AxeHit. Then inside you see it uses IsAlly(), etc. I did not do more than that and I don't know from where it's called if it was your question because it's a virtual function and it's not easy to find references from that.