Remove warns from database when leave a guild

extensions/warn.py

@@ -1,6 +1,6 @@
 import re
 
-from discord import Embed, Forbidden, Member
+from discord import Embed, Forbidden, Member, Guild
 from discord.ext import commands
 from discord.ext.commands import BadArgument
 
@@ -105,6 +105,14 @@ class Warn(commands.Cog):
 
         await ctx.send(embed=embed)
 
+    @commands.Cog.listener()
+    async def on_guild_remove(self, guild: Guild):
+        s = db.Session()
+        for w in s.query(db.Warn).filter(db.Warn.guild == guild.id).all():
+            s.delete(w)
+        s.commit()
+        s.close()
+
 
 def setup(bot):
     logger.info(f"Loading...")