public LinkList build() {
            if (this.linkMap.isEmpty()) {
                return EMPTY;
            }
//             return new LinkList(Map.copyOf(this.linkMap));
            return new LinkList(this.linkMap);
        }
find all out links of fromApplication
@param fromApplication
@return
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/link/LinkList.java