* maths: add weighted_average function
* style: fix blank line after imports
* maths: simplify empty input check in weighted_average
* [pre-commit.ci] auto fixes from pre-commit.com hooks
for more information, see https://pre-commit.ci
* Delete maths/average_weighted.py
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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>