@Restricted(NoExternalUse.class)
    public @NonNull List<VirtualFile> listOnlyDescendants() throws IOException {
        VirtualFile[] children = list();
        List<VirtualFile> result = new ArrayList<>();
        for (VirtualFile child : children) {
            if (child.isDescendant("")) {
                result.add(child);
            }
        }
        return result;
    }
@Test
    public void forAbstractBase_listOnlyDescendants_withoutIllegal() throws Exception {
        File root = tmp.getRoot();
        FileUtils.touch(new File(root, "a"));
        FileUtils.touch(new File(root, "b"));
        VirtualFile virtualRoot = new VirtualFileMinimalImplementation(root);

        assertThat(virtualRoot.listOnlyDescendants(), empty());
    }