What happens when you want to write a set of functions to handle a set of classes? Especially when you are given a class and want to figure out which handler to

What happens when you want to write a set of functions to handle a set of classes? Especially when you are given a class and want to figure out which handler to call dynamically - eg you have FooEvent, should the function be "handle_foo_event", "handle_FooEvent", "HandleFooEvent", or any of several other possibilities?