TypError: 'filter' object is not subscriptable

[HansAchterbahn]

Hi Greg, thanks for your work!
I try to use your plugin but get an error message. Can you help?

Greetings
h8

OS:	Ubuntu 20.04
KiCad Version:	5.1.8-db983349188ubuntu20.04.1, release build
wxWidgets	3.0.4 Unicode and Boost 1.7.1.0
Platform:	Linux 5.4.0-48-generic x86_64, 64 bit

Traceback (bost recent call last):

  File "~/.kicad_plugins/layerviewset.py", line 411, in Run
    filter(lambda w: w.GetTitle().startswith('Pcbnew'),

TypError: 'filter' object is not subscriptable