How to use the discord.ext.commands.Cog.listener function in discord

    @commands.Cog.listener()
    async def on_member_join(self, member):
        """Actually adds the autoassign roles."""
        autoassign_roles = []
        autoassign_role_ids = await \
            self.bot.pg_utils.get_autoassign_roles(member.guild.id)
        if not autoassign_role_ids:
            return
        for role in member.guild.roles:
            if role.id in autoassign_role_ids:
                autoassign_roles.append(role)
        await member.add_roles(*autoassign_roles)

    @commands.Cog.listener()
    async def on_ready(self):
        if not os.path.exists('./tmp/'):
            os.mkdir('./tmp/', mode=0o755)

    @commands.Cog.listener()
    async def on_message(self, message: discord.Message):
        if message.guild is not None or len(message.content) > 1800 or message.author.id == self.bot.user.id:
            return
        ctx: commands.Context = await self.bot.get_context(message)
        if ctx.command is None:
            channel = self.bot.get_channel(Configuration.get_master_var("inbox", 0))
            if channel is not None:
                await channel.send(f"[`{message.created_at.strftime('%c')}`] {message.author} (`{message.author.id}`) said: {message.clean_content}")
            for attachement in message.attachments:
                await channel.send(attachement.url)

    @Cog.listener()
    async def on_message(self, message: Message) -> None:
        """Check new message event for messages to the checkpoint channel & process."""
        if message.channel.id != Channels.verification:
            return  # Only listen for #checkpoint messages

        if message.author.bot:
            # They're a bot, delete their message after the delay.
            # But not the periodic ping; we like that one.
            if message.content != PERIODIC_PING:
                await message.delete(delay=BOT_MESSAGE_DELETE_DELAY)
            return

        # if a user mentions a role or guild member
        # alert the mods in mod-alerts channel
        if message.mentions or message.role_mentions:
            log.debug(

    @commands.Cog.listener()
    async def on_message(self, message):
        log.debug("message from {0!r} in channel {1!r}.".format(message.author, message.channel))
        a, b, c, d = (
            not message.content.startswith('"'),
            message.author.id in self.always_speak_users_by_channel[message.channel.id],
            message.author.voice is not None and message.author.voice.channel is not None,
            message.author != self.bot.user,
        )
        log.debug("always speak bools are: {} {} {} {}".format(a, b, c, d))
        if a and b and c and d:
            log.debug("Always speaking for {}".format(message.author))
            await self.speak_aloud(message, message.content)

    @commands.Cog.listener()
    async def on_ready(self):
        asyncio.create_task(self._cache_data())

	@Cog.listener()
	async def on_message_discarded(self, message):
		''' Trigger the calculator when the message is prefixed by "==" '''
		async def send(*args, **kwargs):
			msg = await message.channel.send(*args, **kwargs)
			await core.blame.set_blame(self.bot.keystore, msg, message.author)
			return msg
		arg = message.content
		if len(arg) > 2 and \
		   arg.startswith('==') and \
		   arg[2] not in '=<>+*/!@#$%^&' and \
		   'results from bdsmtest.org' not in arg.lower() and \
		   await self.bot.settings.resolve_message('f-calc-shortcut', message):
			if not await self.bot.settings.resolve_message('c-calc', message):
				raise core.settings.DisabledCommandByServerOwner
			await self.perform_calculation(arg.strip()[2:], message, send)

	@commands.Cog.listener()
	async def on_unloaded_extension(self, ext):
		# Called to shut things down
		if not self._is_submodule(ext.__name__, self.__module__):
			return
		self.is_current = False
		for task in self.loop_list:
			task.cancel()

	@commands.Cog.listener()
	async def on_loaded_extension(self, ext):
		# See if we were loaded
		if not self._is_submodule(ext.__name__, self.__module__):
			return
		self.bot.loop.create_task(self.start_loading())

    @Cog.listener()
    async def on_message(self, msg: Message) -> None:
        """
        Detect poorly formatted Python code in new messages.

        If poorly formatted code is detected, send the user a helpful message explaining how to do
        properly formatted Python syntax highlighting codeblocks.
        """
        parse_codeblock = (
            (
                msg.channel.id in self.channel_cooldowns
                or msg.channel.id in self.channel_whitelist
            )
            and not msg.author.bot
            and len(msg.content.splitlines()) > 3
        )