func (f *FakeKeyring) Lookup(image string) ([]AuthConfig, bool) {
	return f.auth, f.ok
}

// UnionDockerKeyring delegates to a set of keyrings.
type UnionDockerKeyring []DockerKeyring

// Lookup implements the DockerKeyring method for fetching credentials based on image name.
// return each credentials
func (k UnionDockerKeyring) Lookup(image string) ([]AuthConfig, bool) {
	authConfigs := []AuthConfig{}
	for _, subKeyring := range k {