Creating stable repository in Ubuntu 16.04

Dear Team,

I tried to create stable repository using the following command

sudo add-apt-repository
“deb [arch=amd64] https://download.docker.com/linux/ubuntu/dists/$(lsb_release -cs)/stable”

But I got an error saying IndexError : pieces[2].strip()

Please help to resolve this.

Thanks & Regards
Surya Kumar