Fix 337

[xiki-tempula]

• Warning issued when the series is None for statistical_inefficiency
• ValueError issued when df and series for statistical_inefficiency doesn't have the same length

[codecov[bot]]

Codecov Report

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

Comparison is base (1360a0d) 98.70% compared to head (b152d54) 98.71%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #338 +/- ## ======================================= Coverage 98.70% 98.71% ======================================= Files 28 28 Lines 1860 1864 +4 Branches 402 404 +2 ======================================= + Hits 1836 1840 +4 Misses 2 2 Partials 22 22 ```

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[orbeckst]

@xiki-tempula looks good as it is but if you want to add the logger back then please do. Please squash-merge whenever you're ready.