adds get_KFE method to PMatEKFAC

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and project coverage change: +0.01 :tada:

Comparison is base (930996b) 93.42% compared to head (576b538) 93.44%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #54 +/- ## ========================================== + Coverage 93.42% 93.44% +0.01% ========================================== Files 29 29 Lines 3378 3386 +8 ========================================== + Hits 3156 3164 +8 Misses 222 222 ``` | Flag | Coverage Δ | | |---|---|---| | unittests | `93.44% <100.00%> (+0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Thomas+George#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/tfjgeorge/nngeometry/pull/54?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Thomas+George) | Coverage Δ | | |---|---|---| | [nngeometry/object/pspace.py](https://codecov.io/gh/tfjgeorge/nngeometry/pull/54?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Thomas+George#diff-bm5nZW9tZXRyeS9vYmplY3QvcHNwYWNlLnB5) | `92.32% <100.00%> (+0.10%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Thomas+George). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Thomas+George)

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