def __init__(self, in_dict, values=(), clear=False, **kwargs):
        if isinstance(in_dict, basestring):
            in_dict = _importer(in_dict)
        self.in_dict = in_dict
        # support any argument supported by dict(...) constructor
        self.values = dict(values)
        self.values.update(kwargs)
        self.clear = clear
        self._original = None