@NotNull
  @Override
  protected PsiElementPredicate getElementPredicate() {
    return new PsiElementPredicate() {
      @Override
      public boolean satisfiedBy(@NotNull PsiElement element) {
        if (!(element instanceof GrLiteral)) return false;

        final Object value = ((GrLiteral)element).getValue();
        return value instanceof String && ((String)value).length() == 1;
      }
    };
  }
@NotNull
  @Override
  protected PsiElementPredicate getElementPredicate()