command line - Permanently unset environment variable SUMO_HOME

Previously I installed sumo and set environment variable SUMO_HOME by adding SUMO_HOME='/usr/share/sumo' in /etc/environment.

Now I have uninstalled sumo and want to unset env var SUMO_HOME, I tried this:

1. $ unset SUMO_HOME


2. https://askubuntu.com/a/624958/645099

As in 2nd point I opened these files:

/etc/environment
/etc/profile
~/.profile

~/.bashrc

I searched for SUMO_HOME in these files. I found it in /etc/environment as I added previously, I removed that line, restarted the system.

But again if I type:
$ echo $SUMO_HOME

I get output:
/usr/share/sumo

How can I permanently unset it's value ?

My commands and outputs:

1. check sumo path and SUMO_HOME env. variable

$ whereis sumo

sumo: /usr/bin/sumo /usr/share/sumo /usr/share/man/man1/sumo.1.gz

$ echo $SUMO_HOME
/usr/share/sumo

2. removing sumo

$sudo apt-get remove sumo

Reading package lists... Done
Building dependency tree       
Reading state information... Done
The following packages were automatically installed and are no longer required:
  libmono-addins-gui0.2-cil libmono-addins0.2-cil libmono-posix4.0-cil
  libmono-sharpzip4.84-cil libmono-system-core4.0-cil
Use 'sudo apt autoremove' to remove them.

The following packages will be REMOVED:
  sumo
0 upgraded, 0 newly installed, 1 to remove and 390 not upgraded.
After this operation, 53.0 MB disk space will be freed.
Do you want to continue? [Y/n] y
(Reading database ... 233311 files and directories currently installed.)
Removing sumo (1.3.1+dfsg1-7) ...
Processing triggers for mime-support (3.60ubuntu1) ...
Processing triggers for desktop-file-utils (0.23-1ubuntu3.18.04.1) ...
Processing triggers for man-db (2.8.3-2) ...

Processing triggers for gnome-menus (3.13.3-11ubuntu1) ...

3. again check sumo path and SUMO_HOME env. variable

$ whereis sumo
sumo: /usr/share/sumo


$echo $SUMO_HOME 
/usr/share/sumo

4. unset SUMO_HOME

$ unset SUMO_HOME


$ echo $SUMO_HOME 
No outpout

5. restart system




6. again check sumo path and SUMO_HOME env. variable

$ whereis sumo
sumo: /usr/share/sumo

$echo $SUMO_HOME 
/usr/share/sumo

Why it's still showing same ?