Update model.py

src/models/model.py

@@ -136,3 +136,8 @@ class PLDataModule(LightningDataModule):
         """ test dataloader """
         return DataLoader(
             self.test_dataset, batch_size=self.batch_size, shuffle=False, num_workers=2
+        )
+
+    def val_dataloader(self):
+        """ validation dataloader """
+        return DataLoader(