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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 _child_as_list(self, pk, ck):
 """Returns a list of values from the child FlatterDict instance with string based integer keys. :param str pk: The parent key :param str ck: The child key :rtype: list """

        return [self._values[pk][ck][k]
                for k in sorted(self._values[pk][ck].keys(),
                                key=lambda x: int(x))]