<PackageReference Include="System.ClientModel" Version="1.12.0" />

System.ClientModel.Primitives.PersistableModelProxyAttribute

Attribute that indicates a proxy Type to use for reading a model. The proxy Type must implement IPersistableModel<T> and have a public or non-public parameterless constructor.
namespace System.ClientModel.Primitives { public sealed class PersistableModelProxyAttribute : Attribute { public Type ProxyType { get; } public PersistableModelProxyAttribute(Type proxyType); } }