Various miscellaneous fixes (#81)

ext/MathOptAIDecisionTreeExt.jl

@@ -87,9 +87,9 @@ julia> MathOptAI.build_predictor(ml_model)
 BinaryDecisionTree{Float64,Int64} [leaves=3, depth=2]
 ```
 """
-function MathOptAI.build_predictor(predictor::DecisionTree.Root)
-    return _tree_or_leaf(predictor.node)
-end
+MathOptAI.build_predictor(p::DecisionTree.Root) = _tree_or_leaf(p.node)
+
+MathOptAI.build_predictor(p::DecisionTree.Node) = _tree_or_leaf(p)
 
 function _tree_or_leaf(node::DecisionTree.Node{K,V}) where {K,V}
     return MathOptAI.BinaryDecisionTree{K,V}(

src/MathOptAI.jl

@@ -36,9 +36,7 @@ Return a `Vector{JuMP.VariableRef}` representing `y` such that
 ## Example
 
 ```jldoctest
-julia> using JuMP
-
-julia> import MathOptAI
+julia> using JuMP, MathOptAI
 
 julia> model = Model();
 
@@ -60,21 +58,15 @@ Subject to
 function add_predictor end
 
 """
-    add_predictor(
-        model::JuMP.Model,
-        predictor::AbstractPredictor,
-        x::Matrix,
-    )::Matrix{JuMP.VariableRef}
+    add_predictor(model::JuMP.Model, predictor, x::Matrix)
 
-Return a `Matrix{JuMP.VariableRef}`, representing `y` such that
-`y[:, i] = predictor(x[:, i])` for each columnn `i`.
+Return a `Matrix`, representing `y` such that `y[:, i] = predictor(x[:, i])` for
+each columnn `i`.
 
 ## Example
 
 ```jldoctest
-julia> using JuMP
-
-julia> import MathOptAI
+julia> using JuMP, MathOptAI
 
 julia> model = Model();
 
@@ -95,11 +87,7 @@ Subject to
  2 x[1,3] + 3 x[2,3] - moai_Affine[1] = 0
 ```
 """
-function add_predictor(
-    model::JuMP.Model,
-    predictor,
-    x::Matrix,
-)::Matrix{JuMP.VariableRef}
+function add_predictor(model::JuMP.Model, predictor, x::Matrix)
     y = map(j -> add_predictor(model, predictor, x[:, j]), 1:size(x, 2))
     return reduce(hcat, y)
 end
@@ -122,9 +110,7 @@ A wrapper type for other predictors that implement a reduced-space formulation.
 ## Example
 
 ```jldoctest
-julia> using JuMP
-
-julia> import MathOptAI
+julia> using JuMP, MathOptAI
 
 julia> model = Model();
 

src/predictors/Affine.jl

@@ -18,9 +18,7 @@ f(x) = A x + b
 ## Example
 
 ```jldoctest
-julia> using JuMP
-
-julia> import MathOptAI
+julia> using JuMP, MathOptAI
 
 julia> model = Model();
 

src/predictors/BinaryDecisionTree.jl

@@ -55,7 +55,7 @@ Subject to
  moai_BinaryDecisionTree_z[3] --> {x[1] ≥ 1}
 ```
 """
-struct BinaryDecisionTree{K,V}
+struct BinaryDecisionTree{K,V} <: AbstractPredictor
     feat_id::Int
     feat_value::K
     lhs::Union{V,BinaryDecisionTree{K,V}}