Remove len magic from moving window

Signed-off-by: cwasicki <126617870+cwasicki@users.noreply.github.com>

RELEASE_NOTES.md

@@ -45,6 +45,7 @@
   - Provide access to `capacity` (maximum number of elements) in `MovingWindow`.
   - Methods to retrieve oldest and newest timestamp of valid samples are added to both.
   - `MovingWindow` exposes underlying buffers `window` method.
+  - `len(window)` and `len(buffer)` should be replaced with `window.count_valid()` and `buffer.count_valid()`, respectively.
   - `OrderedRingBuffer.window`:
     - By default returns a copy.
     - Can also return a view if the window contains `None` values and if `force_copy` is set to `True`.

src/frequenz/sdk/timeseries/_moving_window.py

@@ -315,15 +315,6 @@ def count_valid(self) -> int:
         """
         return self._buffer.count_valid()
 
-    def __len__(self) -> int:
-        """
-        Return the size of the `MovingWindow`s underlying buffer.
-
-        Returns:
-            The size of the `MovingWindow`.
-        """
-        return self.count_valid()
-
     @overload
     def __getitem__(self, key: SupportsIndex) -> float:
         """See the main __getitem__ method.