Yeah I have gotten this multiple times with generics. My current solution is to wrap the subscribable in a class like this (make sure to place this class in the same script as my_subscribable):
my_subscribable_agent<public> := class:
Subscribable<public> : my_subscribable(agent) = my__subscribable(agent){}
And then you can just use the Subscribable object in that class, not ideal having to create those extra classes but it’s okay for now I guess.