title: How do I make the bot respond when someone mentions it? discord.py
body: <p>Here is the code I've tried:</p>
  
  <pre class="lang-py prettyprint-override"><code>@client.event
  async def on_message(message):
      if client.user.mention in message.content.split():
          await client.say("You can type `!vx help` for more info.")
  </code></pre>
  
  <p>But it doesn't seem to be working.</p>