Address stefans review - thanks

tests/test_reader.py

@@ -3,7 +3,7 @@
 import time
 from io import BytesIO
 from pathlib import Path
-from typing import Union
+from typing import List, Union
 
 import pytest
 
@@ -37,6 +37,9 @@
 SAMPLE_ROOT = PROJECT_ROOT / "sample-files"
 
 
+NestedList = Union[int, None, List["NestedList"]]
+
+
 @pytest.mark.parametrize(
     ("src", "num_pages"),
     [("selenium-pypdf-issue-177.pdf", 1), ("pdflatex-outline.pdf", 4)],
@@ -696,15 +699,14 @@ def test_issue604(caplog, strict):
             ]
             assert normalize_warnings(caplog.text) == msg
 
-        def get_dest_pages(x) -> Union[int, None]:
+        def get_dest_pages(x) -> NestedList:
             if isinstance(x, list):
-                r = [get_dest_pages(y) for y in x]
-                return r
+                return [get_dest_pages(y) for y in x]
             else:
-                des_page_number = pdf.get_destination_page_number(x)
-                if des_page_number is None:
-                    return des_page_number
-                return des_page_number + 1
+                destination_page_number = pdf.get_destination_page_number(x)
+                if destination_page_number is None:
+                    return destination_page_number
+                return destination_page_number + 1
 
         out = []