public Builder setGroupedNodeFlag(final NodeFlagPair nodeFlagPair,
                                          final boolean isOn) {
            Objects.requireNonNull(nodeFlagPair);
            if (nodeFlags == null) {
                nodeFlags = EnumSet.noneOf(NodeFlag.class);
            }
            nodeFlagPair.addFlag(isOn, nodeFlags);
            return this;
        }
Sets the presence of nodeFlag in this node's set of {@link NodeFlag}s based on the
value of state.
stroom-core-shared/src/main/java/stroom/explorer/shared/ExplorerNode.java