Grabbed dndbeyond's source code

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

ddb_main/tools/js/smartComponents/Collapsible/CollapsibleHeaderContent/CollapsibleHeaderContent.tsx

@@ -0,0 +1,75 @@
+import * as React from "react";
+
+import CollapsibleHeaderCallout from "../CollapsibleHeaderCallout";
+import CollapsibleHeading from "../CollapsibleHeading";
+
+interface Props {
+  heading: React.ReactNode;
+  metaItems?: Array<React.ReactNode>;
+  callout?: React.ReactNode;
+  className: string;
+}
+
+export default class CollapsibleHeaderContent extends React.PureComponent<
+  Props,
+  {}
+> {
+  static defaultProps = {
+    className: "",
+  };
+
+  renderMetaItems(): React.ReactNode {
+    const { metaItems } = this.props;
+
+    if (!metaItems) {
+      return null;
+    }
+
+    return (
+      <div className="ddbc-collapsible__header-meta">
+        {metaItems.map((item, idx) => (
+          <span className="ddbc-collapsible__header-meta-item" key={idx}>
+            {item}
+          </span>
+        ))}
+      </div>
+    );
+  }
+
+  render() {
+    const { className, heading, callout } = this.props;
+
+    let headingNode: React.ReactNode;
+    if (typeof heading === "string") {
+      headingNode = <CollapsibleHeading>{heading}</CollapsibleHeading>;
+    } else {
+      headingNode = heading;
+    }
+
+    let calloutNode: React.ReactNode;
+    if (typeof callout === "string") {
+      calloutNode = <CollapsibleHeaderCallout value={callout} />;
+    } else {
+      calloutNode = callout;
+    }
+
+    let classNames: Array<string> = [
+      "ddbc-collapsible__header-content",
+      className,
+    ];
+
+    return (
+      <div className={classNames.join(" ")}>
+        <div className="ddbc-collapsible__header-content-primary">
+          {headingNode}
+          {this.renderMetaItems()}
+        </div>
+        {calloutNode && (
+          <div className="ddbc-collapsible__header-content-callout">
+            {calloutNode}
+          </div>
+        )}
+      </div>
+    );
+  }
+}

ddb_main/tools/js/smartComponents/Collapsible/CollapsibleHeaderContent/index.ts

@@ -0,0 +1,3 @@
+import CollapsibleHeaderContent from "./CollapsibleHeaderContent";
+
+export default CollapsibleHeaderContent;