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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 setDecoder(self, decoder):
 """ Sets the client's decoder ``decoder`` should be an instance of a ``json.JSONDecoder`` class """

        if not decoder:
            self._decoder = json.JSONDecoder()
        else:
            self._decoder = decoder
        self._decode = self._decoder.decode