Merge pull request #63 from DilumAluthge/dpa/joint-probabilistic-subtype-of-probabilistic

Add `JointProbabilistic` as a subtype of `Probabilistic`, and add generic function stub for `predict_joint`

Author: ablaom

src/MLJModelInterface.jl

@@ -14,7 +14,8 @@ export LightInterface, FullInterface
 # MLJ model hierarchy
 export MLJType, Model, Supervised, Unsupervised,
        Probabilistic, Deterministic, Interval, Static,
-       UnivariateFinite
+       UnivariateFinite,
+       JointProbabilistic
 
 # parameter_inspection:
 export params
@@ -88,6 +89,8 @@ abstract type      Interval <: Supervised end
 
 abstract type Static <: Unsupervised end
 
+abstract type JointProbabilistic <: Probabilistic end
+
 # ------------------------------------------------------------------------
 # includes
 

src/model_api.jl

@@ -44,6 +44,13 @@ probabilistic supervised models may overload `predict_median`
 """
 function predict_median end
 
+"""
+`JointProbabilistic` supervised models MUST overload `predict_joint`.
+
+`Probabilistic` supervised models MAY overload `predict_joint`.
+"""
+function predict_joint end
+
 """
 unsupervised methods must implement the `transform` operation
 """