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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 fold(self):
 """ Recreate original tensor by folding unfolded_sptensor according toc ``ten_shape``. Returns ------- T : sptensor Sparse tensor that is created by refolding according to ``ten_shape``. """

        nsubs = zeros((len(self.data), len(self.ten_shape)), dtype=np.int)
        if len(self.rdims) > 0:
            nidx = unravel_index(self.row, self.ten_shape[self.rdims])
            for i in range(len(self.rdims)):
                nsubs[:, self.rdims[i]] = nidx[i]
        if len(self.cdims) > 0:
            nidx = unravel_index(self.col, self.ten_shape[self.cdims])
            for i in range(len(self.cdims)):
                nsubs[:, self.cdims[i]] = nidx[i]
        nsubs = [z.flatten() for z in hsplit(nsubs, len(self.ten_shape))]
        return sptensor(tuple(nsubs), self.data, self.ten_shape)