Grabbed dndbeyond's source code

```
~/go/bin/sourcemapper -output ddb -jsurl https://media.dndbeyond.com/character-app/static/js/main.90aa78c5.js
```

ddb_main/node_modules/@mui/private-theming/ThemeProvider/nested.js

@@ -0,0 +1,2 @@
+const hasSymbol = typeof Symbol === 'function' && Symbol.for;
+export default hasSymbol ? Symbol.for('mui.nested') : '__THEME_NESTED__';