def _needed_markup_bot(self):
        """
        Returns the input peer of the bot that's needed for the reply markup.

        This is necessary for :tl:`KeyboardButtonSwitchInline` since we need
        to know what bot we want to start. Raises ``ValueError`` if the bot
        cannot be found but is needed. Returns ``None`` if it's not needed.
        """
        if not isinstance(self.reply_markup, (
                types.ReplyInlineMarkup, types.ReplyKeyboardMarkup)):
            return None

        for row in self.reply_markup.rows:
            for button in row.buttons:
                if isinstance(button, types.KeyboardButtonSwitchInline):
                    if button.same_peer:
                        bot = self.input_sender
                        if not bot:
                            raise ValueError('No input sender')
                    else:
                        try:
                            return self._client._entity_cache[self.via_bot_id]
                        except KeyError:
                            raise ValueError('No input sender') from None