Say goodbye to unmanaged Azure AD accounts for B2B collaboration

Thanks Franck, that did the trick.  I had the graph module installed, but didn't import the entire thing.  I would have expected the get-unmanagedexternaluser command or the overall msidentitytools module to check for and import modules it depends on, and didn't even think about that.  

FWIW, the documentation for the microsoft.graph module recommends against installing that parent module, and instead suggests installing only the sub-modules needed.  I would suggest the msidentitytools module be updated to explicitly list what sub-modules of microsoft.graph are required, and either add a #requires statement listing those specific modules or check for and import them within the functions that use them.