Given the following handler chain code snippet, what will be the output when handler1.handle(15) is called?

Given the following handler chain code snippet, what will be the output when handler1.handle(15) is called?

class Handler:
    def __init__(self, next_handler=None):
        self.next_handler = next_handler
    def handle(self, request):
        if request < 10:
            return "Handled by handler1"
        elif self.next_handler:
            return self.next_handler.handle(request)
        else:
            return "Not handled"

handler3 = Handler()
handler2 = Handler(handler3)
handler1 = Handler(handler2)