Create a Csr without edge weights using build:

>>> import AtCoder.Internal.Csr qualified as C
>>> let csr = build' 3 $ VU.fromList @(Int, Int) [(0, 1), (0, 2), (0, 3), (1, 2), (2, 3)]
>>> csr `C.adj` 0
[1,2,3]

>>> csr `C.adj` 1
[2]

>>> csr `C.adj` 2
[3]

Create a Csr with edge weights with build and retrieve edge with edgeW:

>>> import AtCoder.Internal.Csr qualified as C
>>> let csr = build 3 $ VU.fromList @(Int, Int, Int) [(0, 1, 101), (0, 2, 102), (0, 3, 103), (1, 2, 112), (2, 3, 123)]
>>> csr `C.adjW` 0
[(1,101),(2,102),(3,103)]

>>> csr `C.adjW` 1
[(2,112)]

>>> csr `C.adjW` 2
[(3,123)]