Name and document some types

Author: SpecLad

cvat/apps/engine/media_extractors.py

@@ -241,8 +241,12 @@ def __getitem__(self, idx: int):
 
         return value
 
-
 class IMediaReader(ABC):
+    # In both of these tuples, the first element is either the path to the frame or its contents.
+    # In ImageFrame, the second element is the path to the frame.
+    ImageFrame: TypeAlias = tuple[str | io.BytesIO, str]
+    VideoFrame: TypeAlias = tuple[av.VideoFrame, None]
+
     def __init__(
         self,
         *,
@@ -262,7 +266,7 @@ def __init__(
         self._dimension = dimension
 
     @abstractmethod
-    def __iter__(self) -> Iterator[tuple[Any, str | None]]:
+    def __iter__(self) -> Iterator[ImageFrame] | Iterator[VideoFrame]:
         pass
 
     @abstractmethod
@@ -313,7 +317,7 @@ def __init__(
         self._source_paths = sort(source_paths, sorting_method)
         self._sorting_method = sorting_method
 
-    def __iter__(self):
+    def __iter__(self) -> Iterator[IMediaReader.ImageFrame]:
         for i in self.frame_range:
             yield (self.get_image(i), self.get_path(i))
 
@@ -611,7 +615,7 @@ def iterate_frames(
         self,
         *,
         frame_filter: bool | Iterable[int] = True,
-    ) -> Iterator[tuple[av.VideoFrame, None]]:
+    ) -> Iterator[IMediaReader.VideoFrame]:
         """
         If provided, frame_filter must be an ordered sequence in the ascending order.
         'True' means using the frames configured in the reader object.
@@ -658,7 +662,7 @@ def iterate_frames(
                 if next_frame_filter_frame is None:
                     return
 
-    def __iter__(self) -> Iterator[tuple[av.VideoFrame, None]]:
+    def __iter__(self) -> Iterator[IMediaReader.VideoFrame]:
         return self.iterate_frames()
 
     def _read_av_container(self) -> av.container.InputContainer: