if prev_kv is set in the request, the previous key-value pair will be returned.
if prev_kv is set in the request, the previous key-value pair will be returned.
(Since version 0.6.0) Use toPMessage
(Since version 0.6.0) Use getField that accepts a ScalaPB descriptor and returns PValue
if prev_kv is set in the request, the previous key-value pair will be returned.