code: def exists(self, workflow_id):
          
          try:
              db = self._client[self.database]
              col = db[WORKFLOW_DATA_COLLECTION_NAME]
              return col.find_one({"_id": ObjectId(workflow_id)}) is not None
  
          except ConnectionFailure:
              raise DataStoreNotConnected()
docs: Checks whether a document with the specified workflow id already exists.
  
          Args:
              workflow_id (str): The workflow id that should be checked.
  
          Raises:
              DataStoreNotConnected: If the data store is not connected to the server.
  
          Returns:
              bool: ``True`` if a document with the specified workflow id exists.