How would I get a list of packages to allow the user to pick from using only Nuget.VisualStudio?

[maxinfet]

Details about Problem

NuGet product used (NuGet.exe | VS UI | Package Manager Console | dotnet.exe): Nuget.VisualStudio

NuGet version (x.x.x.xxx): 4.7.1.5393

VS version (if appropriate): Visual Studio 2017

OS version (i.e. win10 v1607 (14393.321)): win10 v1803 (17134.228)

I am migrating a internal vsix that was developed against Visual Studio 2013 to work with Visual Studio 2017 and to work with PackageReference instead of package.config. This extension allows the user to pick from stacks of nuget packages to install from our internal nuget repository. I am unsure how I would get a list of packages from our nuget feed using the Nuget.VisualStudio package though. Previously we used Nuget.Core with Visual Studio 2013 but with Nuget.VisualStudio is specifically says in the documentation not to reference any other nuget dlls. How would I go about getting a list of packages with just Nuget.VisualStudio?