Use Union[set, frozenset] for internal consistency.

Author: rwgk

include/pybind11/cast.h

@@ -889,7 +889,7 @@ struct handle_type_name<dict> {
 };
 template <>
 struct handle_type_name<anyset> {
-    static constexpr auto name = const_name("set | frozenset");
+    static constexpr auto name = const_name("Union[set, frozenset]");
 };
 template <>
 struct handle_type_name<set> {

tests/test_pytypes.py

@@ -121,7 +121,7 @@ def test_set(capture, doc):
     assert m.anyset_contains({"foo"}, "foo")
 
     assert doc(m.get_set) == "get_set() -> set"
-    assert doc(m.print_anyset) == "print_anyset(arg0: set | frozenset) -> None"
+    assert doc(m.print_anyset) == "print_anyset(arg0: Union[set, frozenset]) -> None"
 
 
 def test_frozenset(capture, doc):