[ENH] Naive Bayes: Implement predict, fix predict_storage

[janezd]

Implement predict to:

• avoid numpy warning about passing generator to sum
• loop over columns instead of over rows (usually better + more friendly to pandas sometime in the future)
• natively support sparse matrices

predict_storage now calls predict when possible.

predict_storage also didn't work for Instance. Fixed.

Includes

• Code changes
• Tests

[codecov]

Codecov Report

Merging #3540 into master will increase coverage by 0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #3540      +/-   ##
==========================================
+ Coverage   83.95%   83.97%   +0.01%     
==========================================
  Files         370      370              
  Lines       66876    66920      +44     
==========================================
+ Hits        56146    56193      +47     
+ Misses      10730    10727       -3

[markotoplak]

Ok, I like the change.

But why did you decide not route Instance (transformed to Table now) through predict also? If I do it, I see that code to compute probabilities in predict_storage is not run anymore. :)

We should hardcode some actual probabilities into tests. We do not have any test that checks actual results (comparing CA does not count; these tests should be removed, I think).

[janezd]

@markotoplak, I routed Instance through predict and wrote tests that actually check probabilities against those I computed manually.

[janezd]

I removed almost all existing tests but I kept the testing of CA as an (admittedly insensitive) sanity check.

[markotoplak]

Good to have good tests (I did not redo your calculations though), thanks.

It must have been a little late while you were coding this. :) I added two commits. I added the code from the last commit just for my testing, but then I added it, because it makes tests more explicit.

[janezd]

Thanks. I somehow thought I've done this correctly. (But I have no good explanation for assert_not_called in tests. :))

[markotoplak]

Please check if I did something stupid and then merge at will (you can also rebase if you want).