DM-45899: Write a Task to compute Ex for TEx

[PFLeget]

See https://rubinobs.atlassian.net/browse/DM-45899 for more informations.

[arunkannawadi]

There's actually a guide on how to transfer code between packages: https://developer.lsst.io/stack/transferring-code.html#transferring-code-between-packages

Although the history is minimal, it'd be a good practice to follow this procedure.

[arunkannawadi]

The transfer branch should move the code as it was. Suggested doc changes and updating the default values to correspond to treecorr v4.3 should happen after the transfer branch is merged to the ticket branch.

[arunkannawadi]

Are the default values in TreecorrConfig suitable for the metric calculation? I don't quite remember what binning values we settled on, and what the default ones would be. ComputeExPsfConfig should probably have a setDefaults method that would set it to the nbins, min_sep, max_sep and units values appropriately.

[arunkannawadi]

I suspect this needs an explicit validate method that calls self.treecorr.validate. Because TreecorrConfig is not a ConfigClass of a sub task, I am fairly certain that it will never be validated.

[arunkannawadi]

There also needs to be a setDefaults method here that sets the min_sep, max_sep and either nbins or bin_size as appropriate here corresponding to the requirements. @jmeyers314 - what was the binning we settled on finally for TEx computations?

[PFLeget]

For the TEx computations and default parameters, I chose to put the default parameters here instead.

I have the feeling this is a better place, but I can be wrong.

Also, I followed what is written in this doc for the default value.

[PFLeget]

For the validate, I tried in the unit test and putting wrong value in ComputeExPsfConfig (min_sep>max_sep) for example and it triggered the validate from TreecorrConfig. Do I need to do more than that?

[arunkannawadi]

I think it'd be best to put it here, given that i) we might want to run this dynamically outside of computeSummaryStats and ii) it makes sense for this class to have its own defaults for treecorr rather than computeSummaryStats setting them.

[arunkannawadi]

Same comment as in analysis_tools PR - start the commit messages with upper case. Good to go after you set the defaults here in setDefaults.