sad_robot:

I already tried killall python & killall jupyter


Try passing the -9 flag to killall, so that it sends the stronger SIGKILL which cannot be blocked. E.g. killall -9 jupyter.
Killing all python processes may not be advisable, since you may end up disrupting non-ML programs. The better idea is to find the PIDs of your ML python programs using ps -u $USER and killing only the right ones using kill -9 <PID of the python process that you want to kill>.