def is_instagram_story_url(url: str) -> bool:
    return "instagram.com/stories" in url

VIDEO_SUFFIXES = ('.mp4', '.mov', '.mkv')
IMAGE_SUFFIXES = ('.jpg', '.jpeg', '.png', '.webp')

from typing import Optional

def extract_instagram_username(url: Optional[str]) -> Optional[str]:
    # Поддержка:
    # https://www.instagram.com/stories/USERNAME/...
    # https://www.instagram.com/USERNAME/
    try:
        base = url.split("?")[0].strip("/")
        parts = base.split("/")
        if "instagram.com" not in url:
            return None
        if "stories" in parts:
            i = parts.index("stories")
            if i + 1 < len(parts):
                return parts[i + 1]
        # профиль
        host_idx = 0
        for i, p in enumerate(parts):
            if "instagram.com" in p:
                host_idx = i
                break
        if host_idx + 1 < len(parts):
            candidate = parts[host_idx + 1]
            if candidate and candidate not in ("stories", "reel", "p", "tv"):
                return candidate
    except Exception:
        return None
    return None