ValidateCreateDocumentTypeCommand(CreateDocumentTypeCommand cmd)
 => from x in ValidateNonNull(cmd)
 from y in ValidateDocumentTypeName(x.Name)
 select cmd;
 public Try <Validation <Error, DocumentTypeDto> > Execute(CreateDocumentTypeCommand cmd)
 => ()
 => from x in ValidateCreateDocumentTypeCommand(cmd)
 let y                 = CreateDocumentTypeFrom(x)
                 let z = repository.Create(y)
                         select z.ToDocumentTypeDto();