title: @bot.event in a cog discord.py
body: <p>I was wondering if it is possible to use @bot.event
  in a cog for discord.py. I have tried doing     </p>
  
  <pre><code>@self.bot.event
  async def on_member_join(self, ctx, member):
      channel = discord.utils.get(member.guild.channels, name='general')
      await channel.send("hello")
  </code></pre>
  
  <p>in my cog class, but I get the error </p>
  
  <pre><code>NameError: name 'self' is not defined
  </code></pre>
  
  <p>even though I define self.bot in my __init __.</p>
  
  <p>Is there a different way of doing bot.event in cogs, or is it just not possible?</p>