MaybeNullAttribute
Specifies that an output may be null even if the corresponding type disallows it.
namespace System.Diagnostics.CodeAnalysis
{
[AttributeUsage(AttributeTargets.Property | AttributeTargets.Field | AttributeTargets.Parameter | AttributeTargets.ReturnValue, Inherited = false)]
internal sealed class MaybeNullAttribute : Attribute
{
}
}