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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def insert(self, database, key, value, callback=None):
 """ Insert an item into the given database. :param database: The database into which to insert the value. :type database: .BlobDatabaseID :param key: The key to insert. :type key: uuid.UUID :param value: The value to insert. :type value: bytes :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=InsertCommand(key=key.bytes, value=value)),
                                        callback))