```ts
/** A label with one surrounding pair of brackets removed. */
export function unwrapLabel(label: string): string {
  if (!label.startsWith("[")) {
    return label;
  }
  const end = label.lastIndexOf("]");
  if (end === -1) {
    throw new Error("No matching closing bracket found");
  }
  return label.slice(0, end);
}
```