code: func (c *KeyPageIterator) Next(ctx context.Context) (*KeyPage, error) {
  	kp := new(KeyPage)
  	err := c.p.Next(ctx, kp)
  	if err != nil {
  		return nil, err
  	}
  	c.p.SetNextPageURI(kp.NextPageURI)
  	return kp, nil
  }
docs: // Next returns the next page of resources. If there are no more resources,
  // NoMoreResults is returned.