code: def add(self, payload=None):
          
          try:
              db = self._client[self.database]
              col = db[WORKFLOW_DATA_COLLECTION_NAME]
              return str(col.insert_one({
                  DataStoreDocumentSection.Meta:
                      payload if isinstance(payload, dict) else {},
                  DataStoreDocumentSection.Data: {}
              }).inserted_id)
  
          except ConnectionFailure:
              raise DataStoreNotConnected()
docs: Adds a new document to the data store and returns its id.
  
          Args:
              payload (dict): Dictionary of initial data that should be stored
                  in the new document in the meta section.
  
          Raises:
              DataStoreNotConnected: If the data store is not connected to the server.
  
          Returns:
              str: The id of the newly created document.