keys.go
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
}
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
}
// Next returns the next page of resources. If there are no more resources,
// NoMoreResults is returned.