datastore/metadata.go
func keyNames(keys []*Key) []string {
	n := make([]string, 0, len(keys))
	for _, k := range keys {
		n = append(n, k.StringID())
	}
	return n
}
func keyNames(keys []*Key) []string {
	n := make([]string, 0, len(keys))
	for _, k := range keys {
		n = append(n, k.StringID())
	}
	return n
}
// keyNames returns a slice of the provided keys' names (string IDs).