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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 update(self, mapping, prefix=""):
 """ Set the values of multiple keys at once. :param dict mapping: Mapping of keys to values :param str prefix: Optional prefix to apply to all keys in `mapping` before setting """

        for k, v in mapping.items():
            self.set("%s%s" % (prefix, k), v)