code: func IsAllowedVersion(v unversioned.GroupVersion) bool {
  	if len(envRequestedVersions) == 0 {
  		return true
  	}
  	_, found := envRequestedVersions[v]
  	return found
  }
docs: // IsAllowedVersion returns if the version is allowed by the KUBE_API_VERSIONS
  // environment variable. If the environment variable is empty, then it always
  // returns true.