Update special_tokens_map.json

special_tokens_map.json

@@ -19,5 +19,12 @@
     "normalized": true,
     "rstrip": false,
     "single_word": true
+  },
+  "pad_token": {
+    "content": "<unk>",
+    "lstrip": false,
+    "normalized": true,
+    "rstrip": false,
+    "single_word": true
   }
 }