dia-shapes software package provides Diagram editor (additional shapes), 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 dia-shapes
dia-shapes is installed in your system.
Make ensure the dia-shapes package were installed using the commands given below,
$ sudo dpkg-query -l | grep dia-shapes *
You will get with dia-shapes package name, version, architecture and description in a table
| Distro | Debian 9 stretch |
| Section | Graphics |
| Package | dia-shapes |
| Version | 0.6.0-3 |
| Description | Diagram editor (additional shapes) |
| Sub Section | Graphics |