@NotNull
 private String addUniqueField(@NotNull String name) {
   List<String> existNames = fieldNames.get(name);
   if (existNames == null) {
     existNames = new LinkedList<String>();
     fieldNames.put(name, existNames);
   }
   String suffix = existNames.isEmpty() ? "" : "$" + existNames.size();
   String newName = name + suffix;
   existNames.add(newName);
   return newName;
 }