ENH: seqcoll.to_fasta supports block_size

[rmcar17]

Addresses #1795

[rmcar17]

Looks like Python 3.9 is not supported by setup-python on macos-14 (actions/setup-python#850).
A result of the rollout to macos-14, may need to downgrade to macos-13 for now,

[ZeroIntensity]

macos-12 is what macos-latest used to point to, maybe it's a better idea to just use that.

[rmcar17]

Thanks Zero for your suggestion, think either one may have been good enough for our purposes. Looks like it's been resolved now anyways, so we'll be moving back to latest.

[coveralls]

Pull Request Test Coverage Report for Build 8843278136

Details

• 6 of 6 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 91.724%

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Totals
Change from base Build 8843240525:	0.003%
Covered Lines:	29669
Relevant Lines:	32346

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💛 - Coveralls

[GavinHuttley]

Awesome, thank you!