Cannot call the API using complex params about python-wialon HOT 2 CLOSED

from wialon import Wialon
from wialon import WialonError

try:
    wialon_api = Wialon()
    result = wialon_api.token_login(token=token)
    wialon_api.sid = result['eid']

    params = {
        "spec": {
            "itemsType": "avl_unit",
            "propName": "sys_name",
            "propValueMask": "*",
            "sortType": "sys_name"
        },
        "force": 1,
        "flags": 1,
        "from": 0,
        "to": 0
    }
    result = wialon_api.core_search_items(**params)

    wialon_api.core_logout()

    print str(result)
except WialonError as e:
    print str(e)