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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def init(self, dict_or_str, val=None, warn=True):
 """initialize one or several options. Arguments --------- `dict_or_str` a dictionary if ``val is None``, otherwise a key. If `val` is provided `dict_or_str` must be a valid key. `val` value for key Details ------- Only known keys are accepted. Known keys are in `CMAOptions.defaults()` """

        # dic = dict_or_key if val is None else {dict_or_key:val}
        self.check(dict_or_str)
        dic = dict_or_str
        if val is not None:
            dic = {dict_or_str:val}

        for key, val in dic.items():
            key = self.corrected_key(key)
            if key not in CMAOptions.defaults():
                # TODO: find a better solution?
                if warn:
                    print('Warning in cma.CMAOptions.init(): key ' +
                        str(key) + ' ignored')
            else:
                self[key] = val

        return self