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I would rename it Pairwise.

See the samber/ro implem: https://ro.samber.dev/docs/operator/combining#pairwise

Please write 2 implementations:

• core package -> returns [][]T or []T2[T, T]
• it/ package -> returns iter.Seq[[]T] or iter.Seq[T2[T, T]]

Using iter.Seq2 does not seem a good idea here, since first argument of Seq2 is expected to be a key.

I would use T2 tuples instead of simple slices []T.