Returns the number of worker nodes.

        Returns
        -------
        size :int
            The number of worker nodes.

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