docs: private static void delDefault(Tree<Node> tree){
  		if(!tree.isLeaf()){
  			for(int i=0;i<tree.children.size();i++){
  				if(isDefault(tree.getChild(i))){
  					tree.removeChild(i); 
  				}
  			}
  			for(int i=0;i<tree.children.size();i++){
  				delDefault(tree.getChild(i));
  			}
  		}	
  	}