message: Format collection.ts
diff: @@ -75,7 +75,7 @@ export class Collection<K, V> extends Map<K, V> {
  reduce<T>(
  callback: (accumulator: T, value: V, key: K) => T,
  - initialValue?: T
  + initialValue?: T,
  ): T {
  let accumulator: T = initialValue!;
  