public void move(int nodeNum, SpanList target) {
        SpanNode node = children().remove(nodeNum);
        if (node != null) {
            //we found the node
            node.setParent(null);
            resetCachedFromAndTo();
            target.add(node);
        }
    }
Moves a child of this SpanList to another SpanList.

@param nodeNum the index of the node to move
@param target the SpanList to add the node to
@throws IndexOutOfBoundsException if the given index is out of range
document/src/main/java/com/yahoo/document/annotation/SpanList.java