Backport PR #48943 on branch 1.5.x (REGR: ExcelWriter.book not settable)
Backport PR #48943: REGR: ExcelWriter.book not settable
cc @rhshadrach could you have a look? The typing failure looks legit This PR got checked with mypy 0.971; the main PR got checked with 0.981. Locally, I'm seeing the same - mypy flags this as an issue with 0.971 but not 0.981. I get the same behavior with the OP code from this issue back from 2017: https://github.com/python/mypy/issues/4165.

Since 1.5.x is pinned with mypy 0.971, I'm thinking we add a `type: ignore` for just the backport; that make sense? Yep makes sense, thx for investigating 