Update README.md

README.md

@@ -1,11 +1,26 @@
-This dataset is based on the "cumulative" configuration of the MultiWoz 2.2 dataset available also on the [HuggingFace Hub](https://huggingface.co/datasets/multi_woz_v22). Therefore, the system and user utterances, the active intents, and the services are exactly the same.
+This dataset is based on the "cumulative" configuration of the MultiWoz 2.2 dataset available also on the [HuggingFace Hub](https://huggingface.co/datasets/multi_woz_v22). 
+Therefore, the system and user utterances, the active intents, and the services are exactly the same.
 
 In addition to the data present in version 2.2, this dataset contains, for each dialogue turn, the annotations from versions 2.1, 2.3, and 2.4.
 
+
 NOTE:
 
   - Each dialogue turn is composed of a system utterance and a user utterance, in this exact order
   
   - The initial system utterance is filled in with the `none` string
  
-  - In the last dialogue turn is always the system that greets the user; this last turn is kept and the user utterance is filled in with the `none` string (usually during evaluation this dialogue turn is not considered)
+  - In the last dialogue turn is always the system that greets the user; this last turn is kept and the user utterance is filled in with the `none` string (usually during evaluation this dialogue turn is not considered)
+  
+  - To be able to save data as an arrow file you need to "pad" the states to all have the same keys. To do this the None value is introduced. Therefore, when you load it back it is convenient to have a way to remove the "padding".
+  
+  In order to do so, a function like the following can help
+  
+  ```python 
+  def remove_empty_slots(state: Union[Dict[str, Union[List[str], None]], None]) -> Union[Dict[str, List[str]], None]:
+
+    if state is None:
+        return None
+
+    return {k: v for k, v in state.items() if v is not None}
+  ```