public List<CustomerPurchase> LoadData(string filename)
        {
            Dictionary<int, Dictionary<int, CustomerPurchase>> trainingData = new Dictionary<int, Dictionary<int, CustomerPurchase>>();
            using (var sr = new StreamReader(filename))
            {
                var reader = new CsvReader(sr);

                //CSVReader will now read the whole file into an enumerable
                IEnumerable<CustomerPurchase> records = reader.GetRecords<CustomerPurchase>();
                return records.ToList();
            }