+/// be `core::any::Any` (also known as `std::any::Any`), but there are other choices:
+///
+/// - If you want the entire map to be cloneable, use `CloneAny` instead of `Any`; with that, you
+/// can only add types that implement `Clone` to the map.
+/// - You can add on `+ Send` or `+ Send + Sync` (e.g. `Map<dyn Any + Send>`) to add those auto
+/// traits.
+///
+/// Cumulatively, there are thus six forms of map:
+///
+/// - <code>[Map]<dyn [core::any::Any]></code>, also spelled [`AnyMap`] for convenience.
+/// - <code>[Map]<dyn [core::any::Any] + Send></code>
+/// - <code>[Map]<dyn [core::any::Any] + Send + Sync></code>
+/// - <code>[Map]<dyn [CloneAny]></code>
+/// - <code>[Map]<dyn [CloneAny] + Send></code>
+/// - <code>[Map]<dyn [CloneAny] + Send + Sync></code>