human
Solve the following python programming problem given the following code:
def _list_filesystems(reactor, pool) : 
    'Get a listing of all filesystems on a given pool.

    :param pool: A `flocker.volume.filesystems.interface.IStoragePool`
        provider.
    :return: A ``Deferred`` that fires with an iterator, the elements
        of which are ``tuples`` containing the name and mountpoint of each
        filesystem.
    ' 
    listing = zfs_command (reactor, [b'list', b'-d', b'1', b'-H', b'-p', b'-o', b'name,mountpoint,refquota', pool]) 
    def listed(output, pool) : 
        for line in output.splitlines () : 
            (name, mountpoint, refquota) = line.split (b'\t') 
            name = name [(len (pool) + 1) :] 
            if name : 
                refquota = int (refquota.decode ('ascii')) 
                if (refquota == 0) : 
                    refquota = None 
(yield _DatasetInfo (dataset = name, mountpoint = mountpoint, refquota = refquota)) 
listing.addCallback (listed, listing) 
    return listing 

    
    

    Fix the buggy line: listing.addCallback (listed, listing)
assistant
#Here is Python code to fix the buggy line: listing.

listing.addCallback (listed, pool)