public Builder addTag(final String tag) {
            if (!NullSafe.isBlankString(tag)) {
                if (this.tags == null) {
                    this.tags = new HashSet<>();
                }
                this.tags.add(tag);
            }
            return this;
        }
Add a single tag to the builder
stroom-core-shared/src/main/java/stroom/explorer/shared/ExplorerNode.java