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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 _get_all_volumes_paths(conn):
    '''
    Extract the path and backing stores path of all volumes.

    :param conn: libvirt connection to use
    '''
    volumes = [vol for l in [obj.listAllVolumes() for obj in conn.listAllStoragePools()] for vol in l]
    return {vol.path(): [path.text for path in ElementTree.fromstring(vol.XMLDesc()).findall('.//backingStore/path')]
            for vol in volumes if _is_valid_volume(vol)}