Remove messages from lease management.

def remove(self, items):
        """Remove messages from lease management."""
        # Remove the ack ID from lease management, and decrement the
        # byte counter.
        for item in items:
            if self._leased_messages.pop(item.ack_id, None) is not None:
                self._bytes -= item.byte_size
            else:
                _LOGGER.debug("Item %s was not managed.", item.ack_id)

        if self._bytes < 0:
            _LOGGER.debug("Bytes was unexpectedly negative: %d", self._bytes)
            self._bytes = 0