'Calculate the id numbers covered by config word :attr:`id_cfg`.
.. note:: This is a `classmethod`.
:param id_cfg: A hexadecimal config word of id selections.
:type id_cfg: int
:return: ID numbers covered by config word.
:rtype: list'

@classmethod
def get_ids(cls, id_cfg):

    cfg = bin(id_cfg)[:1:(-1)]
    ids = []
    for (i, id_en) in enumerate(cfg):
        if int(id_en):
            ids.append((1 << i))
    return ids
