"0 8-21/3,21 * * *" raises Exception

[pheanex]

I guess the following should not raise and needs fixing?

~ $python -m venv venv
~ $. venv/bin/activate
(venv) ~ $pip install cron-descriptor
Collecting cron-descriptor
  Downloading cron_descriptor-1.4.5-py3-none-any.whl (50 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 50.4/50.4 kB 1.0 MB/s eta 0:00:00
Installing collected packages: cron-descriptor
Successfully installed cron-descriptor-1.4.5

[notice] A new release of pip available: 22.2.1 -> 24.2
[notice] To update, run: pip install --upgrade pip
(venv) ~ $python3
Python 3.10.6 (main, Aug 15 2022, 10:11:08) [GCC 11.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from cron_descriptor import get_description
>>> print(get_description("0 8-21/3,21 * * *"))
Traceback (most recent call last):
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 117, in get_full_description
    time_segment = self.get_time_of_day_description()
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 189, in get_time_of_day_description
    hours_description = self.get_hours_description()
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 273, in get_hours_description
    return self.get_segment_description(
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 458, in get_segment_description
    description = get_interval_description_format(segments[1]).format(get_single_item_description(segments[1]))
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 276, in <lambda>
    lambda s: self.format_time(s, "0"),
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 554, in format_time
    hour = int(hour_expression)
ValueError: invalid literal for int() with base 10: '3,21'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 652, in get_description
    return descriptor.get_description(DescriptionTypeEnum.FULL)
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 104, in get_description
    return choices.get(description_type, self.get_seconds_description)()
  File "/venv/lib/python3.10/site-packages/cron_descriptor/ExpressionDescriptor.py", line 136, in get_full_description
    raise FormatException(description)
cron_descriptor.Exception.FormatException

Syntax seems legit, see i.e. here

[pheanex]

And also "0 10 [1,2,3,4]"

[pheanex]

Coming from the django-celery-beat issue btw