<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def _cleanup_buffer(self):
        '''
        Periodically cleanup the buffer.
        '''
        if not self._buffer:
            return
        while True:
            time.sleep(60)
            log.debug('Cleaning up buffer')
            items = self._buffer.items()
            # The ``items`` function should also cleanup the buffer
            log.debug('Collected items')
            log.debug(list(items))