Fix simulation reaching different states when started from different snaphots.

src/data/mod.rs

@@ -1,5 +1,9 @@
 //! Data structures modified with guaranteed deterministic behavior after deserialization.
 
+pub use self::maybe_serializable_data::MaybeSerializableData;
+
 pub mod arena;
 pub(crate) mod graph;
+pub(crate) mod hashmap;
+mod maybe_serializable_data;
 pub mod pubsub;