Methods shouldn't start with ``get``.  If you didn't want to get a result you wouldn't be calling the method.

This also so far doesn't have anything to do with nonces, so maybe it shouldn't include or_nonce.

Alternatively, if abstract base classes are used for capability discovery and this no longer needs to take an api argument, this could just be a .iv attribute (or reuse .initialization_vector) and nonces can be handled by a different attribute.