private Validation <Error, CreateAnnotationCommand> ValidateCreateAnnoationCommand(CreateAnnotationCommand cmd)
 => from x in ValidateNonNull(cmd)
 from y in ValidateFromDocumentId(x.FromDocumentId)
 from z in ValidateToDocumentTypeId(x.ToDocumentTypeId)
 from a in ValidateToEntityId(x.ToEntityId)
 from b in ValidateToNumber(x.ToNumber)
 from c in ValidateToPublicationYear(x.ToPublicationYear)
 from d in ValidateAnnotationTypeId(x.AnnotationTypeId)
 select x;
 public Try <Validation <Error, AnnotationDto> > Execute(CreateAnnotationCommand cmd)
 => ()
 => from x in ValidateCreateAnnoationCommand(cmd)
 let y = repository.Create(x)
         select y.ToAnnotationDto();