docs: private Map<URI, Set<URI>> addMapFilePrefix(final Map<URI, Set<URI>> map) {
          final Map<URI, Set<URI>> res = new HashMap<>();
          for (final Map.Entry<URI, Set<URI>> e: map.entrySet()) {
              final URI key = e.getKey();
              final Set<URI> newSet = new HashSet<>(e.getValue().size());
              for (final URI file: e.getValue()) {
                  newSet.add(tempFileNameScheme.generateTempFileName(file));
              }
              res.put(key.equals(ROOT_URI) ? key : tempFileNameScheme.generateTempFileName(key), newSet);
          }
          return res;
      }