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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 load_from_data(self, data, with_undefined=False):
 """Load index structure. :param with_undefined: Load undefined keys as well :type with_undefined: bool """

        if with_undefined:
            defined_values, undefined_values = data
        else:
            defined_values = data
            undefined_values = None
        self._index = defaultdict(list, defined_values)
        self._reverse_index = defaultdict(list)
        for key, values in self._index.items():
            for value in values:
                self._reverse_index[value].append(key)
        if undefined_values:
            self._undefined_keys = {key: True for key in undefined_values}
        else:
            self._undefined_keys = {}