Class _DefaultOptionDict

traitlets/config/loader.py:742–777

Like the default options dict but acts as if all --Class.trait options are predefined

class _DefaultOptionDict(dict):  # type:ignore[type-arg]
    """Like the default options dict

    but acts as if all --Class.trait options are predefined
    """

    def _add_kv_action(self, key: str) -> None:
        self[key] = _KVAction(
            option_strings=[key],
            dest=key.lstrip("-").replace(".", _DOT_REPLACEMENT),
            # use metavar for display purposes
            metavar=key.lstrip("-"),
        )

    def __contains__(self, key: t.Any) -> bool:
        if "=" in key:
            return False
        if super().__contains__(key):
            return True

        if key.startswith("-") and class_trait_opt_pattern.match(key):
            self._add_kv_action(key)
            return True
        return False

    def __getitem__(self, key: str) -> t.Any:
        if key in self:
            return super().__getitem__(key)
        else:
            raise KeyError(key)

    def get(self, key: str, default: t.Any = None) -> t.Any:
        try:
            return self[key]
        except KeyError:
            return default


class _KVArgParser(argparse.ArgumentParser):