I found that in the NX-OS 9.2.1 module Cisco-NX-OS-device.yang there is an error in description field in line 102933; it erroneously contains '\' at the end of the line, which confuses libyang YANG parser. This error in the model was fixed in release 9.2.3. In order to address this issue I copied corrected module file to default repository under $USER/.ydk/188.8.131.52/. Then I ran your script and it failed again, but this time due to RPC error. The issue with your script is that it requests entire system config and oper data, and apparently the device choked on it. Then I modified the script to get just one leaf 'systemuptime' and that worked well.
Here is my script:
from ydk.models.cisco_nx_os import Cisco_NX_OS_device as device from ydk.services import CRUDService from ydk.providers import NetconfServiceProvider from ydk.filters import YFilter