Getting columns for a connection not working

[Kaif3007]

I have a redshift connection and i am using python SDK to list all columns of that connection like this:

res = sdk.connection_columns(connection_name="kaifred").

But its returning 500 error:
b'{"message":"An error has occurred.","documentation_url":"https://cloud.google.com/looker/docs/r/err/4.0/500/get/connections/:connection_name/columns"}'

I tried other APIs like connection_tables, connection_databases etc, they are working fine.
I am using 4.0 APIs

sdk = looker_sdk.init40()