SharePoint On-Premises Provisioing Site Collections using Office Dev PnP Core

Hi

Has anyone seen any samples on how to create an on-premises  Site Collection in an OfficeDevPnP Template.  I would of expected to see a method like ProvisioningTemplate.SiteCollection.Add().  But I dont see one.  I can see ProvisioingTemplate AddContentType() and <pnp:SiteCollection> (https://github.com/OfficeDev/PnP-Provisioning-Schema/blob/master/ProvisioningSchema-2016-05.md#sitecollection? )

I suspect that its just a ListCollection in OfficeDevPnP.Core.Framework.Provisioning.Model.

Thanks

Nigel