@dataclass
class BaseConfig:
    """Mixin to allow converting to EFB Config dataclasses from various
       types using classmethods."""

    def __init__(self, *args, **kwargs):
        if args and isinstance(args[0], str):
            argdict = json.loads(args[0])
        elif args and isinstance(args[0], dict):
            argdict = args[0]
        else:
            argdict = kwargs

        for k in self.__annotations__:
            self.__dict__[k] = argdict[k]


@dataclass(init=False)
class UFMConfig(BaseConfig):
    """Base UFM Config, used by the EFB class."""
    init_mem: Path
    zero_mem: bool
    start_page: int
    num_pages: int