@Override void addSources(double weight,Map<Source,SourceNode> sources) {
        for (T child : children)
            child.addSources(weight*getScore(),sources);
    }
This returns the children of this node in the intent tree.
This is never null. Children can be added and removed from this list to modify this node.
container-search/src/main/java/com/yahoo/search/intent/model/ParentNode.java