private void clear() {
        for (Link link : this.linkList) {
            if (!link.isLinked()) {
                link.getLinkedCallTree().remove();
            }
        }
    }
@author netspider
@author emeroad
@author jaehong.kim
web/src/main/java/com/navercorp/pinpoint/web/calltree/span/SpanAligner.java