code: func NamespacedBy(val string) Namespace {
  	if ns, found := namespaces[val]; found {
  		return ns
  	}
  	for p, ns := range prefixNamespaces {
  		if strings.HasPrefix(val, p) {
  			return ns
  		}
  	}
  	return UnknownNamespace
  }
docs: // NamespacedBy returns the namespace of the Linux kernel for a sysctl, or
  // UnknownNamespace if the sysctl is not known to be namespaced.