public void Sanity()
{
var builder = new ElementMetadata.Builder();
builder.AddElement <SomeElement>()
.AddAttribute(0, "s", a => a.Str, a =>
{
});
var data = builder.Build();
var element = new Metadata.ElementState(data);
ref var str = ref element.Attributes.GetProperty(nameof(SomeElement.Str)).Value;