Add missing type annotation

app.py

@@ -1,5 +1,6 @@
 import colorsys
 import gc
+from collections.abc import Iterator
 
 import cv2
 import gradio as gr
@@ -95,10 +96,10 @@ def pastel_color_for_prompt(prompt_text: str) -> tuple[int, int, int]:
 
 
 class AppState:
-    def __init__(self):
+    def __init__(self) -> None:
         self.reset()
 
-    def reset(self):
+    def reset(self) -> None:
         self.video_frames: list[Image.Image] = []
         self.inference_session = None
         self.video_fps: float | None = None
@@ -119,7 +120,7 @@ class AppState:
         self.pending_box_start_obj_id: int | None = None
         self.active_tab: str = "point_box"
 
-    def __repr__(self):
+    def __repr__(self) -> str:
         return f"AppState(video_frames={len(self.video_frames)}, video_fps={self.video_fps}, masks_by_frame={len(self.masks_by_frame)}, color_by_obj={len(self.color_by_obj)})"
 
     @property
@@ -346,7 +347,7 @@ def _get_prompt_for_obj(state: AppState, obj_id: int) -> str | None:
     return None
 
 
-def _ensure_color_for_obj(state: AppState, obj_id: int):
+def _ensure_color_for_obj(state: AppState, obj_id: int) -> None:
     """Assign color to object based on its prompt if available, otherwise use object ID."""
     prompt_text = _get_prompt_for_obj(state, obj_id)
 
@@ -595,7 +596,7 @@ def _get_active_prompts_display(state: AppState) -> str:
     return "**Active prompts:** None"
 
 
-def propagate_masks(GLOBAL_STATE: gr.State):
+def propagate_masks(GLOBAL_STATE: gr.State) -> Iterator[tuple[AppState, str, dict]]:
     if GLOBAL_STATE is None:
         return GLOBAL_STATE, "Load a video first.", gr.update()
 
@@ -861,7 +862,7 @@ def reset_session(GLOBAL_STATE: gr.State) -> tuple[AppState, Image.Image, int, i
     return GLOBAL_STATE, preview_img, slider_minmax, slider_value, status, active_prompts
 
 
-def _on_video_change_pointbox(GLOBAL_STATE: gr.State, video):
+def _on_video_change_pointbox(GLOBAL_STATE: gr.State, video: str | dict) -> tuple[AppState, dict, Image.Image, str]:
     GLOBAL_STATE, min_idx, max_idx, first_frame, status = init_video_session(GLOBAL_STATE, video, "point_box")
     return (
         GLOBAL_STATE,
@@ -871,7 +872,7 @@ def _on_video_change_pointbox(GLOBAL_STATE: gr.State, video):
     )
 
 
-def _on_video_change_text(GLOBAL_STATE: gr.State, video):
+def _on_video_change_text(GLOBAL_STATE: gr.State, video: str | dict) -> tuple[AppState, dict, Image.Image, str, str]:
     GLOBAL_STATE, min_idx, max_idx, first_frame, status = init_video_session(GLOBAL_STATE, video, "text")
     active_prompts = _get_active_prompts_display(GLOBAL_STATE)
     return (