docs: def delete(self, database, key, callback=None):
          """
          Delete an item from the given database.
  
          :param database: The database from which to delete the value.
          :type database: .BlobDatabaseID
          :param key: The key to delete.
          :type key: uuid.UUID
          :param callback: A callback to be called on success or failure.
          """
          token = self._get_token()
          self._enqueue(self._PendingItem(token, BlobCommand(token=token, database=database,
                                                             content=DeleteCommand(key=key.bytes)),
                                          callback))