add warning comment

vision_agent/utils/video.py

@@ -76,6 +76,10 @@ def frames_to_bytes(
  return buffer_bytes
 
 
+# WARNING: this cache is cache is a little dangerous because if the underlying video
+# contents change but the filename remains the same it will return the old file contents
+# but for vision agent it's unlikely to change the file contents while keeping the
+# same file name and the time savings are very large.
 @lru_cache(maxsize=8)
 def extract_frames_from_video(
  video_uri: str, fps: float = 1.0