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/base/utils/appendOwnerState.js

@@ -0,0 +1,24 @@
+import _extends from "@babel/runtime/helpers/esm/extends";
+import { isHostComponent } from './isHostComponent';
+
+/**
+ * Type of the ownerState based on the type of an element it applies to.
+ * This resolves to the provided OwnerState for React components and `undefined` for host components.
+ * Falls back to `OwnerState | undefined` when the exact type can't be determined in development time.
+ */
+
+/**
+ * Appends the ownerState object to the props, merging with the existing one if necessary.
+ *
+ * @param elementType Type of the element that owns the `existingProps`. If the element is a DOM node or undefined, `ownerState` is not applied.
+ * @param otherProps Props of the element.
+ * @param ownerState
+ */
+export function appendOwnerState(elementType, otherProps, ownerState) {
+  if (elementType === undefined || isHostComponent(elementType)) {
+    return otherProps;
+  }
+  return _extends({}, otherProps, {
+    ownerState: _extends({}, otherProps.ownerState, ownerState)
+  });
+}