code: func ExpectedCode(codes ...codes.Code) *CallOption {
  	return &CallOption{
  		grpc.EmptyCallOption{},
  		func(o *Options) {
  			o.expectedCodes = append(o.expectedCodes, codes...)
  		},
  	}
  }
docs: // ExpectedCode can be used to indicate that given non-OK codes may appear
  // during normal successful call flow, and thus they must not be logged as
  // erroneous.
  //
  // Only affects local logging, nothing else.