discord.py cogs not loading code example

Example: how to load a all cogs automatically discord.py

# bot file
import os
from discord.ext import commands

bot = commands.Bot(command_prefix='.')
# I am assuming that you have a test.py cog in a cogs folder
bot.load_extension('cogs.test') # this is good but you can make it better

for filename in os.listdir('./cogs'):
  if filename.endswith('.py'):
    bot.load_extension(f'cogs.{filename[:-3]}')
    
  else:
    print(f'Unable to load {filename[:-3]}')
    
bot.run(token)