fix: revert _get_by_id to private

src/textual/_node_list.py

@@ -63,7 +63,7 @@ class NodeList(Sequence):
         """
         return self._nodes.index(widget)
 
-    def get_by_id(self, widget_id: str) -> Widget | None:
+    def _get_by_id(self, widget_id: str) -> Widget | None:
         """Get the widget for the given widget_id, or None if there's no matches in this list"""
         return self._nodes_by_id.get(widget_id)
 

src/textual/widget.py

@@ -365,7 +365,7 @@ class Widget(DOMNode):
             NoMatches: if no children could be found for this ID
             WrongType: if the wrong type was found.
         """
-        child = self.children.get_by_id(id)
+        child = self.children._get_by_id(id)
         if child is None:
             raise NoMatches(f"No child found with id={id!r}")
         if expect_type is None: