Arguments included in the one parameter can not be optional

[ErikKalkoken]

When we have a task like this:

@celery.task(base=QueueOnce, once={"keys": ["alpha"], "graceful": True})
def example(alpha=None):
    ...

And you call the task without the optional argument like this:

example.delay()

You get an error in celery_once. Apparently, optional arguments are not supported in this context.

Traceback (most recent call last):
  File "/home/erik/python/projects/aa-dev/venv/lib/python3.10/site-packages/celery/app/trace.py", line 569, in trace_task
    task_after_return(
  File "/home/erik/python/projects/aa-dev/venv/lib/python3.10/site-packages/celery_once/tasks.py", line 140, in after_return
    key = self.get_key(args, kwargs)
  File "/home/erik/python/projects/aa-dev/venv/lib/python3.10/site-packages/celery_once/tasks.py", line 129, in get_key
    key = queue_once_key(self.name, call_args, restrict_to)
  File "/home/erik/python/projects/aa-dev/venv/lib/python3.10/site-packages/celery_once/helpers.py", line 71, in queue_once_key
    restrict_kwargs = {key: kwargs[key] for key in restrict_to}
  File "/home/erik/python/projects/aa-dev/venv/lib/python3.10/site-packages/celery_once/helpers.py", line 71, in <dictcomp>
    restrict_kwargs = {key: kwargs[key] for key in restrict_to}
KeyError: 'alpha'

This should at least be mentioned in the README or better yet it should be implemented.