Type annotations for reactive(monotonic) in the tutorial?

[lauralindzey]

I needed a timer in the app I'm building, so I was delighted that your tutorial includes one.

However, I'm stuck on what the proper type annotation is for start_time = reactive(monotonic).
I directly copied my implementation from stopwatch05.py, about which mypy also complains:

$ mypy stopwatch05.py 
stopwatch05.py:12: error: Need type annotation for "start_time"  [var-annotated]
stopwatch05.py:12: error: Argument 1 to "reactive" has incompatible type "Callable[[], float]"; expected "Callable[[], <nothing>]"  [arg-type]
Found 2 errors in 1 file (checked 1 source file)

[davep]

The proper type for start_time would be reactive[float]:

diff --git a/docs/examples/tutorial/stopwatch05.py b/docs/examples/tutorial/stopwatch05.py
index 19f6366f7..66a2162a2 100644
--- a/docs/examples/tutorial/stopwatch05.py
+++ b/docs/examples/tutorial/stopwatch05.py
@@ -9,7 +9,7 @@ from textual.widgets import Button, Footer, Header, Static
 class TimeDisplay(Static):
     """A widget to display elapsed time."""
 
-    start_time = reactive(monotonic)
+    start_time: reactive[float] = reactive(monotonic)
     time = reactive(0.0)
 
     def on_mount(self) -> None:

The reason is start_time is using monotonic as a dynamic default and monotinic returns a float. This also explains why mypy will complain about start_time but not time in the example, as it can easily infer the type of time.