apt-venv software package provides apt virtual environment, you can install in your Debian 9 (Stretch) by running the commands given below on the terminal,
$ sudo apt-get update $ sudo apt-get install apt-venv
apt-venv is installed in your system.
Make ensure the apt-venv package were installed using the commands given below,
$ sudo dpkg-query -l | grep apt-venv *
You will get with apt-venv package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Administration Utilities |
| Package | apt-venv |
| Version | 1.0.0-1 |
| Description | apt virtual environment |
| Sub Section | admin |