<PackageReference Include="Microsoft.Extensions.Configuration.Abstractions" Version="10.0.0-preview.7.25380.108" />

System.Diagnostics.CodeAnalysis.DisallowNullAttribute

Specifies that null is disallowed as an input even if the corresponding type allows it.
namespace System.Diagnostics.CodeAnalysis { internal sealed class DisallowNullAttribute : Attribute { public DisallowNullAttribute(); } }