Identity Weighting Matrix

[sidd3888]

Added the identity weighting matrix to the MSM estimation:

• First change made is to the get_weighting_matrix() function to allow for the identity matrix
• Second change permits "identity" as a valid option for weights in estimate_msm()

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (b77deb8) 92.98% compared to head (2fef810) 92.98%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #477 +/- ## ======================================= Coverage 92.98% 92.98% ======================================= Files 193 193 Lines 14631 14635 +4 ======================================= + Hits 13605 13609 +4 Misses 1026 1026 ```

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[janosg]

Hi @sidd3888, thank you very much for your Pull Request. The changes are great. There is just one more thing: It would be great to also have a small test case for the get_weighting_matrix with the "identity" option.

Let me know whether you want to add this test or I should do it. If you want to add the test, it should be in this file

[sidd3888]

If I understand the code there correctly, this would require nothing more than just adding "identity" as a possible option (and accordingly altering the test) for the get_weighting_matrix test right? I can add that to this PR right away.

[janosg]

Yes. Thank you so much!