uranusjr edited a comment on issue #21259:
URL: https://github.com/apache/airflow/issues/21259#issuecomment-1027620661
The asterisk is optional in this case. It means `run_after` can only be
called as a keyword argument, while the example code allows the caller to use
it as _either_ positional or keyword. But since the function is always only
called with keyword arguments in Airflow, both syntax will work. The example
code is not wrong.
As for the absolute import issue, unfortunately this is a (somewhat obsecure
and annoying) problem in Python. If you add a directory in `sys.path` via
multiple paths, names imported from different `sys.path` items have different
identities.
```console
$ tree
.
|-- plugins
|-- __init__.py
`-- mod.py
$ cat plugins/mod.py
class A:
pass
$ PYTHONPATH=plugins python -q # Simulate how Airflow loads the plugin
directory.
>>> from plugins.mod import A as AFromAbsolute
>>> from mod import A as AFromPlugin
>>> AFromAbsolute == AFromPlugin
False
```
And since timetable is loaded from plugin, you must import relative to the
plugin directory, or somewhere that’s not related to the plugin directory
hierarchy, such as `site-packages`. There are _probably_ hacks we can use to
work around this, but this kind of “working above” the Python language rules is
not a good idea to me.
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