def __init__(self):
        self._values = {}
        self._loaded_files = []

        # Set the default value of each ``Option``
        for name, opt in self.options().items():
            opt._validate(opt.default)
            self._values[name] = opt.default

        # Call hooks for each Option
        # (This must happen *after* all default values are set so that
        # logging can be properly configured.
        for opt in self.options().values():
            opt._callback(self)