Fix cnv_discordant_read_calls: raise ValueError when no data found

[Jiya873]

This pull request addresses issue #777 where calling cnv_discordant_read_calls with absent data was causing an IndexError instead of the expected ValueError. The changes include:

• Refactoring cnv_discordant_read_calls:
  The empty-data check is now moved outside the inner loop that iterates over the sample sets. If no dataset is found for a contig (or across all contigs), a ValueError is raised with an informative message.

• Updated Tests:
  The relevant tests in test_cnv_data.py have been leveraged to confirm that the expected ValueError is raised in cases where data is absent (e.g., for non-existent sample sets or contigs).

These changes ensure that the API behaves more predictably and makes debugging easier when data is missing.

[jonbrenas]

This looks good, thank you @Jiya873. I am going to shadow this PR to enable the checks.

If you updated test_cnv_data.py, you forgot to push your changed as they are not showing currently.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 2 lines in your changes missing coverage. Please review.

Project coverage is 96.07%. Comparing base (0197957) to head (f56c6d8).
Report is 50 commits behind head on master.

Files with missing lines	Patch %	Lines
malariagen_data/anoph/cnv_data.py	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #781      +/-   ##
==========================================
- Coverage   96.13%   96.07%   -0.06%     
==========================================
  Files          47       47              
  Lines        4683     4689       +6     
==========================================
+ Hits         4502     4505       +3     
- Misses        181      184       +3     

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[Jiya873]

Hi @jonbrenas, I had indeed forgotten to push the updated test_cnv_data.py earlier. I've just pushed the changes now. Please let me know if everything looks good or if further updates are needed.

[jonbrenas]

Thank you @Jiya873. It looks like the tests don't like your monkeypatching. I will try to look at what seems to be the problem ...if you don't beat me to it.

[leehart]

Not sure what state this PR is in?

[jonbrenas]

I think it has been abandoned.

[leehart]

Thanks @jonbrenas . If there's no response after a short time (say, September) then I guess we'll close this. This PR can always be resurrected, if needs be.