You may want the `snapmirror.is_protected` field which would make your query look like this:
for vol in Volume.get_collection(fields="svm,name,state,is_svm_root", **{"snapmirror.is_protected": True}):
print(vol)
Sometimes there are fields in the CLI which are not exposed in the REST API. If there's something you rely on that's not in REST, you may open a case with support to ask that it be added. As a stop-gap in the meantime, you can make use of the CLI passthrough endpoint which allows you to make CLI calls and get the results through the rest interface. In this case it would look like this:
from netapp_ontap import HostConnection
from netapp_ontap.resources import CLI
with HostConnection(...):
response = CLI().execute("volume show", vserver_dr_protection="protected")
for volume in response.http_response.json()["records"]:
print(volume)