def contains(self, data):
        """
        Check if an item has been added to the bloomfilter.

        :param bytes data: a bytestring representing the item to check.
        :returns: a boolean indicating whether or not the item is present in
            the bloomfilter. False-positives are possible, but a negative
            return value is definitive.
        """
        bfo = BitFieldOperation(self.database, self.key)
        for bit_index in self._get_seeds(data):
            bfo.get('u1', bit_index)
        return all(bfo.execute())