message: feature: add HashMap keys method.
diff: @@ -694,6 +694,9 @@ export class HashMap<T, KEY extends string | number = string | number> {
  }
  }
  }
  + keys(): KEY[] {
  + return keys(this.data);
  + }
  // Do not use this method if performance sensitive.
  removeKey(key: KEY) {
  delete this.data[key];
  