code: @NullSafe
    public static ThreadGroup getThreadGroup(Thread thread) {
      return (thread != null ? thread.getThreadGroup() : null);
    }
docs: A null-safe method for getting the Thread's ThreadGroup.
  
  @param thread the Thread from which the ThreadGroup is returned.
  @return the ThreadGroup of the specified Thread or null if the Thread is null.
  @see java.lang.Thread#getThreadGroup()
  @see java.lang.ThreadGroup