public IEnumerable <TOut> WithMapper <TMapper>()
            where TMapper : IMapper <TIn, TOut>, new()
        {
            var mapper = new TMapper();

            return(_EntitiesIn.Select(x => mapper.Map(x)));
        }
        public TOut WithMapper <TMapper>()
            where TMapper : IMapper <TIn, TOut>, new()
        {
            var mapper = new TMapper();

            return(mapper.Map(_EntityIn));
        }