<oslc_cm:message>Unknown attribute id: rtc_cm:type</oslc_cm:message>

my environment is python-3.6 and RTC 6.0.6

I'm trying to run the example script:

from rtcclient.utils import setup_basic_logging
from rtcclient import RTCClient
url = "https://cmis-rtc.de.xxxxx.com:9443/ccm"
username = "XXXXX"
password = "XXXXX"
myclient = RTCClient(url, username, password, ends_with_jazz=False)
myquery = myclient.query
projectarea_name = "Tooling Support"
myquerystr = 'rtc_cm:type="defect"'
#myquerystr = 'oslc_cm:status="Rejected"'
#myquerystr = 'dcterms:type="Issue"'
#myquerystr = 'oslc_cm:inprogress="true"'
returned_prop = "dc:title,dc:identifier,rtc_cm:state"
queried_wis = myquery.queryWorkitems(query_str=myquerystr, projectarea_name=projectarea_name, returned_properties=returned_prop)

whatever I us for myquerystr, the result is always:
Unknown attribute id: xxxx:xxxx

any help appreciated.