Expose derived feature value in model insights

[TuanNguyen27]

Some of the derived features (or engineered features) have human-readable values that could be exposed inside modelInsights for downstream consumption.

[codecov[bot]]

Codecov Report

Merging #484 into master will increase coverage by 0.02%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #484      +/-   ##
==========================================
+ Coverage   87.01%   87.03%   +0.02%     
==========================================
  Files         345      345              
  Lines       11680    11683       +3     
  Branches      378      387       +9     
==========================================
+ Hits        10163    10168       +5     
+ Misses       1517     1515       -2     

Impacted Files	Coverage Δ
...c/main/scala/com/salesforce/op/ModelInsights.scala	93.09% <100.00%> (+0.04%)	:arrow_up:
...force/op/stages/impl/feature/OPMapVectorizer.scala	97.79% <100.00%> (+0.01%)	:arrow_up:
...es/src/main/scala/com/salesforce/op/OpParams.scala	89.79% <0.00%> (+4.08%)	:arrow_up:

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[TuanNguyen27]

LGTM, are there other places where the descriptor value should be passed on?

I did a spot check, i think only OpMapVec was missing this.

[TuanNguyen27]

Yes, what happened with the OpMapVec? Did we miss adding descriptorValue? Also, maybe add one test in ModelInsight when a descriptor value is being added.

There's this line and this line that check for non-empty derivedFeatureValue. However we don't have a test for derivedFeatureValue when it is derived from a Map feature. Is it okay if i just add a check for derivedFeatureValue when it comes from a Map feature ?

[TuanNguyen27]

@leahmcguire @michaelweilsalesforce It's actually tricky to write a test for this change, because the existing tests drop numericMap as a feature...Do you have any suggestions ?