Repository: yt-dlp/yt-dlp
File: yt_dlp/extractor/youtube.py (Python)

Code before:
            if not player_url and not tried_iframe_fallback and require_js_player:
                player_url = self._download_player_url(video_id)
                tried_iframe_fallback = True

            visitor_data = visitor_data or self._extract_visitor_data(master_ytcfg, initial_pr, player_ytcfg)
            data_sync_id = data_sync_id or self._extract_data_sync_id(master_ytcfg, initial_pr, player_ytcfg)

            fetch_po_token_args = {
                'client': client, 'visitor_data': visitor_data, 'video_id': video_id,
                'data_sync_id': data_sync_id if self.is_authenticated else None,
                'player_url': player_url if require_js_player else None,
                'session_index': self._extract_session_index(master_ytcfg, player_ytcfg),
                'ytcfg': player_ytcfg,
            }

            player_po_token = self.fetch_po_token(
                context=_PoTokenContext.PLAYER, **fetch_po_token_args)

            gvs_po_token_func = lambda: self.fetch_po_token(
                context=_PoTokenContext.GVS, **fetch_po_token_args)

            # Fetch an initial PO Token for GVS upfront
            gvs_po_token = gvs_po_token_func()

            require_player_po_token = _PoTokenContext.PLAYER in self._get_default_ytcfg(client).get('PO_TOKEN_REQUIRED_CONTEXTS')
            if not player_po_token and require_player_po_token:
                # TODO: may need to skip player response request. Unsure yet..
                self.report_warning(
                    f'No Player PO Token provided for {client} client, '
                    f'which may be required for working {client} formats. This client will be deprioritized'
                    f'You can manually pass a Player PO Token for this client with --extractor-args "youtube:po_token={client}.player+XXX". '
                    f'For more information, refer to {PO_TOKEN_GUIDE_URL} .', only_once=True)
                deprioritize_pr = True

            require_gvs_po_token = _PoTokenContext.GVS in self._get_default_ytcfg(client).get('PO_TOKEN_REQUIRED_CONTEXTS')
            if not gvs_po_token and require_gvs_po_token and 'missing_pot' in self._configuration_arg('formats'):
                # note: warning with help message is provided later during format processing
                self.report_warning(
                    f'No GVS PO Token provided for {client} client, '
                    f'which may be required for working {client} formats. This client will be deprioritized', only_once=True)
                deprioritize_pr = True

            pr = initial_pr if client == 'web' else None
            try:
                pr = pr or self._extract_player_response(
                    client, video_id,
                    master_ytcfg=player_ytcfg or master_ytcfg,
                    player_ytcfg=player_ytcfg,
                    player_url=player_url,
                    initial_pr=initial_pr,
                    visitor_data=visitor_data,

Review comment (bug):
since we `setdefault` for all clients, we don't need `.get()` and IMO we'd want a key error here to notice if we change things elsewhere and forget to here. I think it's also less taxing to read if we use a var for the required contexts instead of temp var for `require_player_po_token` since we do the same thing below
```suggestion
            po_token_required_contexts = self._get_default_ytcfg(client)['PO_TOKEN_REQUIRED_CONTEXTS']

            if not player_po_token and _PoTokenContext.PLAYER in po_token_required_contexts:
```

Code after:
            fetch_po_token_args = {
                'client': client,
                'visitor_data': visitor_data,
                'video_id': video_id,
                'data_sync_id': data_sync_id if self.is_authenticated else None,
                'player_url': player_url if require_js_player else None,
                'session_index': self._extract_session_index(master_ytcfg, player_ytcfg),
                'ytcfg': player_ytcfg,
            }

            player_po_token = self.fetch_po_token(
                context=_PoTokenContext.PLAYER, **fetch_po_token_args)

            gvs_po_token = self.fetch_po_token(
                context=_PoTokenContext.GVS, **fetch_po_token_args)

            required_pot_contexts = self._get_default_ytcfg(client)['PO_TOKEN_REQUIRED_CONTEXTS']

            if (
                not player_po_token
                and _PoTokenContext.PLAYER in required_pot_contexts
            ):
                # TODO: may need to skip player response request. Unsure yet..
                self.report_warning(
                    f'No Player PO Token provided for {client} client, '
                    f'which may be required for working {client} formats. This client will be deprioritized'
                    f'You can manually pass a Player PO Token for this client with --extractor-args "youtube:po_token={client}.player+XXX". '
                    f'For more information, refer to {PO_TOKEN_GUIDE_URL} .', only_once=True)
                deprioritize_pr = True

            if (
                not gvs_po_token
                and _PoTokenContext.GVS in required_pot_contexts
                and 'missing_pot' in self._configuration_arg('formats')
            ):
                # note: warning with help message is provided later during format processing
                self.report_warning(
                    f'No GVS PO Token provided for {client} client, '
                    f'which may be required for working {client} formats. This client will be deprioritized',
                    only_once=True)
                deprioritize_pr = True

            pr = initial_pr if client == 'web' else None
            try:
                pr = pr or self._extract_player_response(
                    client, video_id,
                    master_ytcfg=player_ytcfg or master_ytcfg,
                    player_ytcfg=player_ytcfg,
                    player_url=player_url,
                    initial_pr=initial_pr,
                    visitor_data=visitor_data,