Add dependencies to management pack with powershell

Hi!

I am trying to use this: http://blogs.msdn.com/b/rslaten/archive/2013/05/09/creating-management-packs-in-scom-2012-with-powershell.aspx

And then add a group to the management pack using this:

http://blogs.msdn.com/b/rslaten/archive/2013/06/06/creating-groups-in-scom-2012-with-powershell.aspx

But to be able to do that the management pack needs to have this dependencies: "Instance Group Library".

I know that dependencie are automatically added to the MP if i add a group in the console, but I need to do it with powershell.

Can someone please help me?