Class DefaultHandler

traitlets/traitlets.py:1287–1293

class DefaultHandler(EventHandler):
    def __init__(self, name: str) -> None:
        self.trait_name = name

    def class_init(self, cls: type[HasTraits], name: str | None) -> None:
        super().class_init(cls, name)
        cls._trait_default_generators[self.trait_name] = self


class HasDescriptors(metaclass=MetaHasDescriptors):