$ sudo apt-get update
$ sudo apt-get install dkim-milter-python 

dkim-milter-python is installed in your system.

Make ensure the dkim-milter-python package were installed using the commands given below,

$ sudo dpkg-query -l | grep dkim-milter-python *

You will get with dkim-milter-python package name, version, architecture and description in a table

dkim-milter-python package basic information: