return false, fmt.Errorf("invalid value of %s: %s, err: %v", apiKey, flagValue, err)
		}
		return boolValue, nil
	}
	return defaultValue, nil
}

// ParseGroups takes in resourceConfig and returns parsed groups.
func ParseGroups(resourceConfig cliflag.ConfigurationMap) ([]string, error) {
	groups := []string{}
	for key := range resourceConfig {
		if _, ok := groupVersionMatchers[key]; ok {
			continue
		}

		// Do not allow only set api/all=false, in such case apiserver startup has no meaning.
		return append(errors, fmt.Errorf("invalid key with only %v=false", resourceconfig.APIAll))
	}

	groups, err := resourceconfig.ParseGroups(s.RuntimeConfig)
	if err != nil {
		return append(errors, err)
	}

	for _, registry := range registries {
		// filter out known groups
		groups = unknownGroups(groups, registry)
	}
	if len(groups) != 0 {