Add MLJ compliant docstrings

[josephsdavid]

Need double check if they go before or after we export the model metadata!

[ablaom]

If you don't use MLJModelInterface.doc_header then it doesn't matter.

[davnn]

Is it supposed that the MLJ docs are defined separately from the model-specific comments, e.g. there would then be https://github.com/OutlierDetectionJL/OutlierDetectionNeighbors.jl/blob/master/src/models/knn.jl#L4 and

OutlierDetectionNeighbors.jl/src/OutlierDetectionNeighbors.jl

Line 239 in 9a8ca8b

`KNNDetector`: Identify anomalies using the distances between an instance and its k nearest neighbors.

?

[codecov]

Codecov Report

Base: 100.00% // Head: 98.89% // Decreases project coverage by -1.10% ⚠️

Coverage data is based on head (9a8ca8b) compared to base (12565d1).
Patch has no changes to coverable lines.

Additional details and impacted files

@@             Coverage Diff             @@
##            master       #3      +/-   ##
===========================================
- Coverage   100.00%   98.89%   -1.11%     
===========================================
  Files            7        7              
  Lines          170      181      +11     
===========================================
+ Hits           170      179       +9     
- Misses           0        2       +2     

Impacted Files	Coverage Δ
src/OutlierDetectionNeighbors.jl	100.00% <ø> (ø)
src/models/dnn.jl	96.29% <0.00%> (-3.71%)	⬇️
src/utils.jl	97.05% <0.00%> (-2.95%)	⬇️
src/models/cof.jl	100.00% <0.00%> (ø)
src/models/lof.jl	100.00% <0.00%> (ø)
src/models/abod.jl	100.00% <0.00%> (ø)

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[ablaom]

I think @josephsdavid should comment here, but I think that's the current proposal - to append to the existing doc-strings. Because you also have a native API, right? However, I think we're open to a different suggestion.

[josephsdavid]

Yes this was my understanding, but I am happy to adjust to however works best!

[ablaom]

@davnn Did you have any further comment on this PR? If not I will go ahead and review for compliance with the spec.

Keen to get this soon as @josephsdavid's GSoC intern finishes imminently.

[davnn]

I would maybe put the docs into an MLJ_docs.jl file or similar, otherwise LGTM, thanks a lot 🙏🏼

[ablaom]

Sorry for not catching this earlier but the current plan is not working out that well. The main problem is that the new docstrings are overwriting the existing ones. This may explain why @josephsdavid has duplicated the "Parameters" section, which ought not to be necessary and is bad for maintenance. It is possible to extend rather than replace a doc-string, by wrapping additions in a new module, but then the additions appear before the existing docstring, which is not what we want here.

In any case, I think splitting the doc string up is ultimately a hack and suggest abandoning that approach. I have added a POC for what I would recommend. @davnn If you would give the okay, then perhaps @josephsdavid still has time to adapt his PR along that line.

Final comment is that the MLJ examples in the current PR look untested - at least I found the ABODDetector example did not work (fixed in my POC).