private void assertCopyOrMoveParameters(final ExplorerTreeNode node,
                                            final ExplorerTreeNode newParent,
                                            final int position,
                                            final ExplorerTreeNode sibling) {
        if (node != null && isPersistent(node)) {
            assertInsertParameters(newParent, sibling, position);
        } else {
            throw new IllegalArgumentException("Node to move is null or not persistent: " + node);
        }
    }
Get the root node containing a particular node, or the node itself if it is a root node.
stroom-explorer/stroom-explorer-impl-db/src/main/java/stroom/explorer/impl/db/ExplorerTreeDaoImpl.java