@Override
  public @Nullable MultiMap<PsiElement, String> findConflicts(ChangeInfo info, Ref<UsageInfo[]> refUsages) {
    final MultiMap<PsiElement, String> conflicts = new MultiMap<>();
    if (info instanceof PyChangeInfo && info.isNameChanged()) {
      final PyFunction function = ((PyChangeInfo)info).getMethod();
      final PyClass clazz = function.getContainingClass();
      if (clazz != null && clazz.findMethodByName(info.getNewName(), true, null) != null) {
        conflicts.putValue(function, RefactoringBundle.message("method.0.is.already.defined.in.the.1",
                                                               info.getNewName(),
                                                               "class " + clazz.getQualifiedName()));
      }
    }
    return conflicts;
  }
@Override
  public @Nullable MultiMap<PsiElement, String> findConflicts(ChangeInfo info, Ref<UsageInfo[]> refUsages)