Revert "delete online Data Getter and Iter"

This reverts commit 9b21071c8d.

fastNLP/core/batch.py

@@ -201,6 +201,19 @@ class TorchLoaderIter(BatchIter):
         self.batch_size = dataset.batch_size
 
 
+class OnlineDataGettter:
+    # TODO
+    pass
+
+
+class OnlineDataIter(BatchIter):
+    # TODO
+    def __init__(self, dataset, batch_size=1, buffer_size=10000, sampler=None, as_numpy=False,
+                 num_workers=0, pin_memory=False, drop_last=False,
+                 timeout=0, worker_init_fn=None, **kwargs):
+        super().__init__()
+
+
 def _to_tensor(batch, field_dtype):
     """