So I know that there is a similar question on stack overflow but it is for discord.js and I use discord.py so can someone tell me (also this is my first question on stack overflow)
Okay so the above one is almost correct. The solution is:
@client.command()
async def something(ctx, target:discord.Member = None):
if target == None:
await ctx.send("You didn't mention anyone!")
else:
await ctx.send(target.mention)
#whatever other code
so it's target:discord.Member = None
instead of target:discord.Member == None
and that async def thingy ofcourse :)