[Python] How to unban a user?

I know how to ban members and I know how to kick them, but I don't know how to unban them. I have the following code which outputs the error:

discord.ext.commands.errors.CommandInvokeError: Command raised an exception: AttributeError: 'generator' object has no attribute 'id'
​

Code:

@bot.command(pass_context=True)
@commands.has_role("Moderator")
async def unban2(ctx):
mesg = ctx.message.content[8:]
banned = client.get_user_info(mesg)
await bot.unban(ctx.message.server, banned)
await bot.say("Unbanned!")

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