Can't update items from project's data

[skica-dev]

>>> from todoist import TodoistAPI
>>> api = TodoistAPI(KEY)
>>> p = api.projects.get_data(2233523660)["items"]
>> item = p[1]
>>> item.update(labels=[new_label_id])
>> item["labels"]
[new_label_id]
>>> api.commit()
>>> api.sync()
>>> item["labels"]
[new_label_id]

Looks fine, hovewer the label (or any other parameter) doesn't update (in API or in webapp):

>>> api1 = TodoistAPI(KEY)
>>> api1.sync()
>> item1 = api1.items.get_by_id(id_of_item)
item1["labels"]
[]

Updating same task got by api.items.get_by_id() works fine.