public IActionResult GetNMRById(int id)
        {
            var prob = _repo.RetrieveNmrProblemById(id);

            if (prob == null)
            {
                return(NotFound(ApiResponse.Error("nmr problem not found")));
            }
            return(Ok(ApiResponse.Success(ResponseUtil.NmrProblemConvert(prob))));
        }