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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 target_key(self, key):
 """Temporarily retarget the client for one call to route specifically to the one host that the given key routes to. In that case the result on the promise is just the one host's value instead of a dictionary. .. versionadded:: 1.3 """

        router = self.connection_pool.cluster.get_router()
        host_id = router.get_host_for_key(key)
        rv = self.target([host_id])
        rv.__resolve_singular_result = True
        return rv