Missing Pipeline and PipelineReader<> types

[keithallenjackson]

I'm trying to target both PowerShell 7+ and Windows PowerShell 5.1 using the PowerShellStandard.Library 5.1 nuget package within my C# project and when I try to build it cannot find any Pipeline related types.

namespace: System.Management.Automation.Runspaces
Missing Types:
Pipeline
PipelineReader<>