docutils.nodes.Node.next_node can return None

See code at https://github.com/docutils/docutils/blob/6d835be25d585e1dce688ef33c3876aa34ba59f0/docutils/docutils/nodes.py#L369:

```python
    def next_node(self,
                  condition: type | Callable[[Node], bool] | None = None,
                  include_self: bool = False,
                  descend: bool = True,
                  siblings: bool = False,
                  ascend: bool = False,
                  ) -> Node | None:
        """
        Return the first node in the iterator returned by findall(),
        or None if the iterable is empty.

        Parameter list is the same as of `findall()`.  Note that `include_self`
        defaults to False, though.
        """
        try:
            return next(self.findall(condition, include_self,
                                     descend, siblings, ascend))
        except StopIteration:
            return None
```

Author: adamtheturtle

stubs/docutils/docutils/nodes.pyi

@@ -89,7 +89,7 @@ class Node:
     @overload
     def next_node(
         self, condition: type[_N], include_self: bool = False, descend: bool = True, siblings: bool = False, ascend: bool = False
-    ) -> _N: ...
+    ) -> _N | None: ...
     @overload
     def next_node(
         self,
@@ -98,7 +98,7 @@ class Node:
         descend: bool = True,
         siblings: bool = False,
         ascend: bool = False,
-    ) -> Node: ...
+    ) -> Node | None: ...
     def validate(self, recursive: bool = True) -> None: ...
     def validate_position(self) -> None: ...