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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 num_workers(self):
 """Returns the number of worker nodes. Returns ------- size :int The number of worker nodes. """

        size = ctypes.c_int()
        check_call(_LIB.MXKVStoreGetGroupSize(self.handle, ctypes.byref(size)))
        return size.value