Detect Flythrough mode in editor script

Hey I've been on some kind of epic journey trying to find answers and came across this looking for the same thing. The information doesn't seem to be listed anywhere, in documentation or forums, and nobody responds (as you can see here).

But I found it:

     (Tools.viewTool == ViewTool.FPS)

With Tools.current you can see which tool is selected, but [flythrough mode / "3D Viewport/Fly Mode" / FPS mode] is different, and you can use that code above to detect it. (They call it a bunch of things inconsistently, makes searching hard).

See also / example:

     Debug.Log(Tools.current);
     Debug.Log(Tools.viewTool);
     Debug.Log(Tools.current == Tool.Transform);