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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 to_json(self):
 """ Returns a json-serialized version of the unit registry """

        sanitized_lut = {}
        for k, v in self.lut.items():
            san_v = list(v)
            repr_dims = str(v[1])
            san_v[1] = repr_dims
            sanitized_lut[k] = tuple(san_v)

        return json.dumps(sanitized_lut)