yesno arg is optional

[CarlFK]

"Given a string mapping values for true, false and (optionally) None, returns one of those strings according to the value:"
​https://docs.djangoproject.com/en/dev/ref/templates/builtins/#yesno

Looking at the code, I see the string is optional.

if arg is None:

arg = ugettext('yes,no,maybe')

​http://code.djangoproject.com/svn/django/trunk/django/template/defaultfilters.py

[Julien Phalip]

Accepted. The documentation could be improved by noting that if no argument is provided then the default is "yes,no,maybe".

[Calvin Spealman]

yesno docs now explain the argument is optional, and the default

[Karen Tracey]

In [17086]:

Fix #17179: Document that yesno filter's default argument is "yes,no,maybe". Thanks CarlFK and calvinspealman.