Example in README not working - unrecognized attribute modifier 'contain'

Inizia con l’esempio di filtraggio nella README e riproduci la sessione Python mostrata usando TaskWarrior. Verifica il modificatore usato nell’esempio confrontandolo con il comando e l’errore risultanti di TaskWarrior; il lavoro è completato quando il filtro documentato non produce più un modificatore di attributo non riconosciuto.

❯ python3
Python 3.8.0 (default, Oct 28 2019, 16:14:01) 
[GCC 8.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from tasklib import TaskWarrior
>>> tw = TaskWarrior('~/.local/share/task')
>>> tw.tasks.filter(tags__contain='passive')
KeyboardInterrupt
>>> tasks = tw.tasks.pending()
>>> tasks.filter(tags__contain='chores')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/janek/daten/projects/_forks/tasklib/tasklib/task.py", line 464, in __repr__
    data = list(self[:REPR_OUTPUT_SIZE + 1])
  File "/home/janek/daten/projects/_forks/tasklib/tasklib/task.py", line 481, in __getitem__
    self._result_cache = list(self)
  File "/home/janek/daten/projects/_forks/tasklib/tasklib/task.py", line 471, in __len__
    self._result_cache = list(self.__iter__())
  File "/home/janek/daten/projects/_forks/tasklib/tasklib/task.py", line 476, in __iter__
    self._result_cache = self._execute()
  File "/home/janek/daten/projects/_forks/tasklib/tasklib/task.py", line 508, in _execute
    return self.backend.filter_tasks(self.filter_obj)
  File "/home/janek/daten/projects/_forks/tasklib/tasklib/backends.py", line 334, in filter_tasks
    for line in self.execute_command(args):
  File "/home/janek/daten/projects/_forks/tasklib/tasklib/backends.py", line 297, in execute_command
    raise TaskWarriorException(error_msg)
tasklib.backends.TaskWarriorException: Using alternate data.location /home/janek/.local/share/task
Configuration override rc.confirmation:no
Configuration override rc.dependency.confirmation:no
Configuration override rc.recurrence.confirmation:no
Configuration override rc.json.array:off
Configuration override rc.bulk:0
Configuration override rc.data.location:/home/janek/.local/share/task
Error: unrecognized attribute modifier 'contain'.
Command used: task rc.confirmation=no rc.dependency.confirmation=no rc.recurrence.confirmation=no rc.json.array=off rc.bulk=0 rc.data.location=/home/janek/.local/share/task export status:'pending' tags.contain:'c,h,o,r,e,s'