# lowered nested block structure in previous design, we can use `vi` inside "inner" block, however, we cannot `compute_at` "inner" outside "outer" because information regarding "vi" is lost.
for i in range(20):
    with block("outer"):
        vi = T.axis.spatial(i, 20)
        for j in range(indptr[i + 1] - indptr[i]):
        with block("inner"):
            vj = T.axis.spatial(j, 10)
            ...

# inherit `vi` from "outer" block in inner block, we can `compute_at` "inner" block outside "outer" and `vi_1` would be re-bound to other iter values.
for i in range(20):
    with block("outer"):
        vi = T.axis.spatial(i, 20)
        for j in range(indptr[i + 1] - indptr[i]):
        with block("inner"):
            vi_1 = T.axis.spatial(vi, 20)
            vj = T.axis.spatial(j, 10)
            ...