convertor from grpc response not implemented

[saeid93]

trafficstars

As mentioned https://github.com/SeldonIO/MLServer/pull/727#discussion_r972003311 the convertor from grpc output is not implemented.

This isn't working as the following line:

from mlserver.grpc.converters import ModelInferResponseConverter
from mlserver.codecs.string import StringRequestCodec

inference_response = ModelInferResponseConverter.to_types(response)

is calling the following, which the inference_response output for the subsequent line of the scripts will be None https://github.com/SeldonIO/MLServer/blob/fac90c83a3536dbbea9e7075c590e33ace424537/mlserver/grpc/converters.py#L301