docs: def _set_buttons(self, chat, bot):
          """
          Helper methods to set the buttons given the input sender and chat.
          """
          if isinstance(self.reply_markup, (
                  types.ReplyInlineMarkup, types.ReplyKeyboardMarkup)):
              self._buttons = [[
                  MessageButton(self._client, button, chat, bot, self.id)
                  for button in row.buttons
              ] for row in self.reply_markup.rows]
              self._buttons_flat = [x for row in self._buttons for x in row]