I was following instructions directly from this link here
to try to install Docker CE on virtual box running Ubuntu 18.04 LTS, but I get the following error:
Error: 'deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable' invalid
The exact command I followed is:
$ sudo add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable"
which was provided in the link above. How can I fix this error?