Adding rate matrix index

[sonachitchyan]

:pencil: Description

Type: infrastructure

This PR addds the NLTEIndexHelper class which has the output rate_matrix_index. This will be used for constructing the rate equation for solving NLTE ionization and NLTE excitation. Index helper returns MultiIndex with atomic number, ion number and whether the species is treated in lte or nlte_ionization. If none of those are the case, it keeps the level number as the third index for further usage in NLTE excitation treatment.

:vertical_traffic_light: Testing

How did you test these changes?

• [x] Testing pipeline
• [ ] Other method (describe)
• [ ] My changes can't be tested (explain why)

:ballot_box_with_check: Checklist

• [x] I requested two reviewers for this pull request
• [ ] I updated the documentation according to my changes
• [ ] I built the documentation by applying the build_docs label

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[codecov[bot]]

Codecov Report

Merging #2132 (0adb313) into master (e3184f4) will decrease coverage by 0.03%. The diff coverage is 40.62%.

:exclamation: Current head 0adb313 differs from pull request most recent head ec8b749. Consider uploading reports for the commit ec8b749 to get more accurate results

@@            Coverage Diff             @@
##           master    #2132      +/-   ##
==========================================
- Coverage   61.63%   61.60%   -0.04%     
==========================================
  Files          75       76       +1     
  Lines        8649     8681      +32     
==========================================
+ Hits         5331     5348      +17     
- Misses       3318     3333      +15     

Impacted Files	Coverage Δ
tardis/plasma/standard_plasmas.py	70.09% <22.22%> (-4.40%)	:arrow_down:
tardis/plasma/properties/rate_matrix_index.py	40.00% <40.00%> (ø)
tardis/plasma/properties/plasma_input.py	100.00% <100.00%> (ø)
tardis/plasma/properties/property_collections.py	100.00% <100.00%> (ø)
tardis/io/util.py	80.50% <0.00%> (+2.51%)	:arrow_up:

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[wkerzendorf]

@sonachitchyan can you update the ddescription of the PR

[wkerzendorf]

@sonachitchyan also adding tests that just load the infrastructure (not even solving it successfully would be great)

[wkerzendorf]

Very nice PR. I think the only thing left is the _new thing.