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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 index(self, key):
 """ Get the index of a given entry, raising an IndexError if it's not present. `key` can be an iterable of entries that is not a string, in which case this returns a list of indices. """

        if is_iterable(key):
            return [self.index(subkey) for subkey in key]
        return self.map[key]