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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 rank(self):
 """ Returns the rank of this worker node. Returns ------- rank : int The rank of this node, which is in range [0, num_workers()) """

        rank = ctypes.c_int()
        check_call(_LIB.MXKVStoreGetRank(self.handle, ctypes.byref(rank)))
        return rank.value