code: private void trainOnInstanceImpl(Instance inst) {
  		if(this.treeRoot == null){
  			this.treeRoot = newLearningNode(this.parallelismHint);
  			this.activeLeafNodeCount = 1;
                          
  		}
  		FoundNode foundNode = this.treeRoot.filterInstanceToLeaf(inst, null, -1);
                  trainOnInstanceImpl(foundNode, inst);
          }
docs: Helper method that represent training of an instance. Since it is decision tree,
  this method routes the incoming instance into the correct leaf and then update the
  statistic on the found leaf.
  @param inst