namespace System.Security
{
    [Obsolete("Code Access Security is not supported or honored by the runtime.", DiagnosticId = "SYSLIB0003", UrlFormat = "https://aka.ms/dotnet-warnings/{0}")]
    public class PermissionSet : ICollection, IEnumerable, IDeserializationCallback, ISecurityEncodable, IStackWalk
    {
        public IPermission? AddPermission(IPermission? perm);
    }
}