code: @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;
      }
docs: Lists only the children that are descendant of the root directory (not necessarily the current VirtualFile).
  Only one level deep.
  
  @return a list of descendant children (files and subdirectories); empty for a file or nonexistent directory
  @throws IOException if this directory exists but listing was not possible for some other reason