Setting busy_status with python-kopano

rdd2

I am trying to create appointments in python-kopano and set their busy_status.

Docs say about busy_status attribute of appointment:

busy_status
Appointment busy status (free, tentative, busy, out_of_office, working_elsewhere or unknown)

But when I try to create an appointment with

appointment = appointments.create_item(
    ...,
    busy_status = 'free',
    ...
)

I get a

  File "./calendar-event-test.py", line 409, in createCalendarEvent
    busy_status = 'busy' 
  File "/usr/lib/python3/dist-packages/kopano/folder.py", line 557, in create_item
    setattr(item, key, val)
AttributeError: can't set attribute

How should I go about setting it? What am I doing wrong?

Thomas