add TupleKey method to convert string key back to tuple

src/types/TupleKey.ts

@@ -16,4 +16,9 @@ export class TupleKey<T extends any[]> {
   valueOf(): string {
     return this.strKey;
   }
+
+  static fromExistingStringKey(strKey: string) {
+    const tuple = strKey.split(separator);
+    return new TupleKey(...tuple);
+  }
 }