def METHOD_NAME(objects):
    """Return tuple of addons for a given sequence of objects."""
    addons = {}
    def _addons(objs):
        """Recursively determine addons that are requested."""
        for addon in objs:
            if addon not in addons:
                if addon.required_addons:
                    _addons(addon.required_addons)
                addons[addon] = None
    _addons(objects)
    return tuple(addons)