code: public alluxio.grpc.ChannelAuthenticationScheme getAuthenticationScheme() {
      alluxio.grpc.ChannelAuthenticationScheme result = alluxio.grpc.ChannelAuthenticationScheme.valueOf(authenticationScheme_);
      return result == null ? alluxio.grpc.ChannelAuthenticationScheme.NOSASL : result;
    }
docs: <code>optional .alluxio.grpc.sasl.ChannelAuthenticationScheme authenticationScheme = 4;</code>