'/Off' keys not culled in _radio_button() and _checkbox()

[remremrem]

line 14 and line 30 in pdf_form_filler.py

if ['/Off'] in keys:

should be

if '/Off' in keys:

[summerswallow]

You could be right. When I get a chance to unit test it. I'll make the change or if you'd like to do a pull request with a unit test to demonstrate that. I'll merge it.