There is a very common pattern for creating optional arguments
when you can't use None:



It's a bit annoying to create this marker objects, and also,
if you try to render a signature of such function, you'll get
something like:

"(*, arg1='spam', arg3=None, arg4=<object object at 0x104be7080>)"

What if we add a standard marker for this use-case:
functools.optional or inspect.Parameter.optional?