docs: protected Map<String, String> getPrefixedProperties(String prefix) {
          Map<String, String> rval = new HashMap<>();
          Iterator<String> keys = getConfig().getKeys();
          while (keys.hasNext()) {
              String key = keys.next();
              if (key.startsWith(prefix)) {
                  String value = getConfig().getString(key);
                  key = key.substring(prefix.length());
                  rval.put(key, value);
              }
          }
          return rval;
      }