<PackageReference Include="Microsoft.Extensions.DependencyInjection.Abstractions" Version="10.0.0-preview.6.25358.103" />

System.Diagnostics.CodeAnalysis.MaybeNullWhenAttribute

Specifies that when a method returns ReturnValue, the parameter may be null even if the corresponding type disallows it.
namespace System.Diagnostics.CodeAnalysis { internal sealed class MaybeNullWhenAttribute : Attribute { public bool ReturnValue { get; } public MaybeNullWhenAttribute(bool returnValue); } }