@Nullable
    private Pair<PsiElement, String> getDictLiteralKey(@NotNull PyKeyValueExpression argument) {
      final PyExpression key = argument.getKey();
      final String keyValue = getKeyValue(key);
      return keyValue != null ? Pair.createNonNull(key, keyValue) : null;
    }
@Nullable
    private Pair<PsiElement, String> getDictLiteralKey(@NotNull PyKeyValueExpression argument)