docs: @CheckReturnValue
    public <NewReqT, NewRespT> Builder<NewReqT, NewRespT> toBuilder(
        Marshaller<NewReqT> requestMarshaller, Marshaller<NewRespT> responseMarshaller) {
      return MethodDescriptor.<NewReqT, NewRespT>newBuilder()
          .setRequestMarshaller(requestMarshaller)
          .setResponseMarshaller(responseMarshaller)
          .setType(type)
          .setFullMethodName(fullMethodName)
          .setIdempotent(idempotent)
          .setSafe(safe)
          .setSampledToLocalTracing(sampledToLocalTracing)
          .setSchemaDescriptor(schemaDescriptor);
    }