another try at #2915

[mergify[bot]]

⚠️ The sha of the head commit of this PR conflicts with #2915. Mergify cannot evaluate rules on this PR. ⚠️

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0.72464% with 137 lines in your changes are missing coverage. Please review.

Project coverage is 81.60%. Comparing base (045b419) to head (5850551).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #2927 +/- ## ========================================== + Coverage 81.31% 81.60% +0.29% ========================================== Files 48 48 Lines 37856 37426 -430 Branches 7295 7232 -63 ========================================== - Hits 30782 30542 -240 + Misses 5653 5466 -187 + Partials 1421 1418 -3 ``` | [Flag](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | Coverage Δ | | |---|---|---| | [c-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `86.21% <ø> (ø)` | | | [lwt-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `80.78% <ø> (ø)` | | | [python-c-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `68.45% <0.72%> (+0.74%)` | :arrow_up: | | [python-tests](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | `98.97% <ø> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev#carryforward-flags-in-the-pull-request-comment) to find out more. | [Files](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927?dropdown=coverage&src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev) | Coverage Δ | | |---|---|---| | [python/tskit/stats.py](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927?src=pr&el=tree&filepath=python%2Ftskit%2Fstats.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev#diff-cHl0aG9uL3Rza2l0L3N0YXRzLnB5) | `35.13% <ø> (+24.79%)` | :arrow_up: | | [python/tskit/trees.py](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927?src=pr&el=tree&filepath=python%2Ftskit%2Ftrees.py&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev#diff-cHl0aG9uL3Rza2l0L3RyZWVzLnB5) | `43.88% <0.72%> (-2.75%)` | :arrow_down: | ... and [2 files with indirect coverage changes](https://app.codecov.io/gh/tskit-dev/tskit/pull/2927/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=tskit-dev)

[benjeffery]

Closing in favour of #2915