There is an updated pull request by tornaria against master on the void-packages repository

https://github.com/tornaria/void-packages mpmath
https://github.com/void-linux/void-packages/pull/42753

python3-mpmath: update to 1.3.0.
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#### Testing the changes
- I tested the changes in this PR: **briefly** (tested with sagemath)

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A patch file from https://github.com/void-linux/void-packages/pull/42753.patch is attached