Make constructor of DecisionContext package private

Author: panhongx

improveai/src/main/java/ai/improve/DecisionContext.java

@@ -14,7 +14,7 @@ public class DecisionContext {
 
     private Map givens;
 
-    public DecisionContext(DecisionModel decisionModel, Map givens) {
+    protected DecisionContext(DecisionModel decisionModel, Map givens) {
         this.decisionModel = decisionModel;
         this.givens = givens;
     }

improveai/src/main/java/ai/improve/DecisionModel.java

@@ -313,7 +313,7 @@ public <T> Decision<T> chooseFrom(List<T> variants, List<Double> scores) {
      * @return An IMPDecision object.
      * */
     public Decision chooseMultiVariate(Map<String, ?> variants) {
-        return new DecisionContext(this, null).chooseMultiVariate(variants);
+        return given(null).chooseMultiVariate(variants);
     }
 
     /**
@@ -331,7 +331,7 @@ public Decision chooseMultiVariate(Map<String, ?> variants) {
      * variant and it's not a List or Map.
      * */
     public Object which(Object... variants) {
-        return new DecisionContext(this, null).which(variants);
+        return given(null).which(variants);
     }
 
     /**