fix bugs of _FDataset of paddle, jittor and oneflow

fastNLP/core/dataloaders/jittor_dataloader/fdl.py

@@ -37,6 +37,12 @@ class _JittorDataset(Dataset):
             item = item.tolist()
         return (item, self.dataset[item])
 
+    def __getstate__(self):
+        return self.__dict__
+
+    def __setstate__(self, state):
+        self.__dict__ = state
+
           
 class JittorDataLoader:
     """

fastNLP/core/dataloaders/oneflow_dataloader/fdl.py

@@ -47,6 +47,12 @@ class _FDataSet:
     def __len__(self) -> int:
         return len(self.dataset)
 
+    def __getstate__(self):
+        return self.__dict__
+
+    def __setstate__(self, state):
+        self.__dict__ = state
+
 
 class OneflowDataLoader(DataLoader):
     """

fastNLP/core/dataloaders/paddle_dataloader/fdl.py

@@ -43,6 +43,15 @@ class _PaddleDataset(Dataset):
         except Exception as e:
             raise e
 
+    def __len__(self) -> int:
+        return len(self.dataset)
+
+    def __getstate__(self):
+        return self.__dict__
+
+    def __setstate__(self, state):
+        self.__dict__ = state
+
 
 class PaddleDataLoader(DataLoader):
     """