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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 _shrink_list(self, shrink):
 """ Shrink list down to essentials :param shrink: List to shrink :type shrink: list :return: Shrunk list :rtype: list """

        res = []

        if len(shrink) == 1:
            return self.shrink(shrink[0])
        else:
            for a in shrink:
                temp = self.shrink(a)

                if temp:
                    res.append(temp)
        return res