baseimage-tutorial-framework/lib/tfw/components/mixins/callback_mixin.py

from functools import partial


class CallbackMixin:
    def __init__(self):
        self._callbacks = []

    def subscribe_callback(self, callback, *args, **kwargs):
        fun = partial(callback, *args, **kwargs)
        self._callbacks.append(fun)

    def unsubscribe_callback(self, callback):
        self._callbacks.remove(callback)

    def _execute_callbacks(self, *args, **kwargs):
        for callback in self._callbacks:
            callback(*args, **kwargs)