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/styled-components/src/utils/determineTheme.js

@@ -0,0 +1,10 @@
+// @flow
+import { EMPTY_OBJECT } from './empties';
+
+type Props = {
+  theme?: any,
+};
+
+export default (props: Props, providedTheme: any, defaultProps: any = EMPTY_OBJECT) => {
+  return (props.theme !== defaultProps.theme && props.theme) || providedTheme || defaultProps.theme;
+};