Align label mapping with imdb dataset

config.json

@@ -17,5 +17,13 @@
   "num_hidden_layers": 1,
   "pad_token_id": 0,
   "type_vocab_size": 2,
-  "vocab_size": 30522
-}
+  "vocab_size": 30522,
+  "label2id": {
+    "neg": 0,
+    "pos": 1
+  },
+  "id2label": {
+    "0": "neg",
+    "1": "pos"
+  }
+}