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/system/esm/memoize.js

@@ -0,0 +1,9 @@
+export default function memoize(fn) {
+  const cache = {};
+  return arg => {
+    if (cache[arg] === undefined) {
+      cache[arg] = fn(arg);
+    }
+    return cache[arg];
+  };
+}