rehash(newCapacity) {
    const newMap = new HashMap(newCapacity);

    this.keysArrayWrapper.forEach((key) => {
      newMap.set(key.content, this.get(key.content));
    });

    // update bucket
    this.buckets = newMap.buckets;
    this.collisions = newMap.collisions;
    // Optional: both `keys` has the same content except that the new one doesn't have empty spaces from deletions
    this.keysArrayWrapper = newMap.keysArrayWrapper;
  }
Rehash means to create a new Map with a new (higher) capacity with the purpose of outgrow collisions.
@param {Number} newCapacity