async_set_fan_mode() got an unexpected keyword argument 'fan_mode'

[syssi]

Changing fan mode from "high" to "medium" - didn't seem to get accepted neither through a beepbeep sound neither through the unit itself it still blows in high:

2018-12-02 12:22:25 ERROR (MainThread) [homeassistant.core] Error doing job: Task exception was never retrieved
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/homeassistant/helpers/service.py", line 277, in _handle_service_platform_call
    await getattr(entity, func)(**data)
TypeError: async_set_fan_mode() got an unexpected keyword argument 'fan_mode'

EDIT: Went back to "heat" from "ventilate" tried changing fan mode to "medium" from "high" again same log as above.

cp. #40 (comment)

@gsotiriou