code: func (s *Sandbox) UserNsPath() string {
  	if s.infraContainer != nil {
  		return fmt.Sprintf("/proc/%v/ns/user", s.infraContainer.State().Pid)
  	}
  	return ""
  }
docs: // UserNsPath returns the path to the user namespace of the sandbox.
  // If the sandbox uses the host namespace, nil is returned