@Override
    void setParent(SpanNodeParent parent) {
        super.setParent(parent);
        for (Children ch : childTrees) {
            ch.setParent(parent);
        }
    }
Returns a modifiable {@link List} of child nodes of the specified subtree.

@param i the index of the subtree to search
@return a modifiable {@link List} of child nodes of the specified subtree
document/src/main/java/com/yahoo/document/annotation/AlternateSpanList.java