Returns the total button count.

def button_count(self):
        """
        Returns the total button count.
        """
        if self._buttons_count is None:
            if isinstance(self.reply_markup, (
                    types.ReplyInlineMarkup, types.ReplyKeyboardMarkup)):
                self._buttons_count = sum(
                    len(row.buttons) for row in self.reply_markup.rows)
            else:
                self._buttons_count = 0

        return self._buttons_count