func (s Schema) mustGetKey(name string) Key {
	key, ok := s[name]
	if !ok {
		panic(fmt.Sprintf("attempt to access unknown key '%s'", name))
	}
	return key
}
func (s Schema) mustGetKey(name string) Key {
	key, ok := s[name]
	if !ok {
		panic(fmt.Sprintf("attempt to access unknown key '%s'", name))
	}
	return key
}
// Get the Key associated with the given name, or panic.