public ExplorerNode getParent(final ExplorerNode child) {
        return NullSafe.get(child, child2 -> childKeyToParentNodeMap.get(getNodeKey(child2)));
    }
//     * Replaces an existing node with the supplied one. The new node will
//     * be linked to the previous node's parent and children. If the key is
//     * not found an exception will be thrown. Intended for changing other properties
//     * of a node, e.g. the alerts on it.
//     *
//     * MUST be done while under an exclusive lock on this model.
//
stroom-explorer/stroom-explorer-impl/src/main/java/stroom/explorer/impl/AbstractTreeModel.java