You might have to uninstall/remove files from docker too. Try doing this:
To remove all docker containers and images:
docker kill $(docker ps -q)
docker rm $(docker ps -aq)
docker rmi $(docker images -q)
This will remove the docker files. But composer will other files too, you have to delete it. I have mentioned commands to delete different files/folders:
Composer cards folder
$ rm -rf ~/.composer
Scripts and tools to create Fabric:
$ rm -rf ~/.fabric-tools
$ sudo rm /usr/local/bin/docker-compose
$ sudo apt-get remove docker-ce
Hope this helps!
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