### Question:
Utils { static boolean canFullyTraverseSubkeyForRename(Object document, String key) { List<String> pathFragments = splitPath(key); String mainKey = pathFragments.get(0); if (pathFragments.size() == 1) { return true; } String subKey = getSubkey(pathFragments, new AtomicReference<>()); Object subObject = getFieldValueListSafe(document, mainKey); if (subObject instanceof Document) { return canFullyTraverseSubkeyForRename(subObject, subKey); } else { return subObject instanceof Missing; } }  static Object getSubdocumentValue(Document document, String key); static Object getSubdocumentValueCollectionAware(Document document, String key); static String getDatabaseNameFromFullName(String fullName); static String getCollectionNameFromFullName(String fullName); static boolean isTrue(Object value); static Number normalizeNumber(Number value); static void markOkay(Document result); static String join(List<?> values, String delimiter); static void changeSubdocumentValue(Object document, String key, Object newValue); static void validateFieldNames(Document document); static Object removeSubdocumentValue(Object document, String key); static String describeType(Object value); static String joinTail(List<String> pathFragments); static String firstFragment(String input); static List<String> splitPath(String input); static String getShorterPathIfPrefix(String path1, String path2); static List<String> collectCommonPathFragments(String path1, String path2); static String getHostName(); static void copySubdocumentValue(Document input, Document result, String key); static final String PATH_DELIMITER; }### Answer:
@Test void testCanFullyTraverseSubkeyForRename() { Document document = json("_id: 1, foo: {bar: 1, bla: 2}, baz: { bar: [ { a:1, b:2} , 2, 3] }"); boolean ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "foo.bar"); assertThat(ableToTraverse).isTrue(); ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "foo.bar.missing"); assertThat(ableToTraverse).isFalse(); ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "foo.missing"); assertThat(ableToTraverse).isTrue(); ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "baz.bar"); assertThat(ableToTraverse).isTrue(); ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "baz.bar.0"); assertThat(ableToTraverse).isFalse(); ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "baz.bar.0.a"); assertThat(ableToTraverse).isFalse(); ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "baz.bar.foo"); assertThat(ableToTraverse).isFalse(); ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "missing"); assertThat(ableToTraverse).isTrue(); ableToTraverse = Utils.canFullyTraverseSubkeyForRename(document, "missing.a"); assertThat(ableToTraverse).isTrue(); }