$ sudo apt-get update
$ sudo apt-get install gir1.2-lightdm-1 

gir1.2-lightdm-1 is installed in your system.

Make ensure the gir1.2-lightdm-1 package were installed using the commands given below,

$ sudo dpkg-query -l | grep gir1.2-lightdm-1 *

You will get with gir1.2-lightdm-1 package name, version, architecture and description in a table

gir1.2-lightdm-1 package basic information: