def _get_used_lun_ids_for_mappings(mappings):
    """Returns used LUNs when provided with mappings."""
    used_luns = set(map(lambda lun: int(lun['lun']), mappings))
    # E-Series uses LUN ID 0 for special purposes and should not be
    # assigned for general use
    used_luns.add(0)
    return used_luns