public Builder addNodeFlag(final NodeFlag nodeFlag) {
            if (nodeFlag != null) {
                if (this.nodeFlags == null) {
                    this.nodeFlags = EnumSet.noneOf(NodeFlag.class);
                }
                NodeFlag.validateFlag(nodeFlag, this.nodeFlags);
                this.nodeFlags.add(nodeFlag);
            }
            return this;
        }
Adds a flag to this node if nodeFlag is not null.
stroom-core-shared/src/main/java/stroom/explorer/shared/ExplorerNode.java