def METHOD_NAME():
    assert get_cep_from_dn(None) is None
    assert get_cep_from_dn("") is None
    assert get_cep_from_dn("cep-") is None
    assert get_cep_from_dn("cep-1a!") is None
    assert get_cep_from_dn("aacep-1a!") is None
    assert get_cep_from_dn("/cep-1a!/") == "1a!"
    assert get_cep_from_dn("aa/cep-1a!/aa") == "1a!"
    assert get_cep_from_dn("aa/cep-/aa") is None
    assert get_cep_from_dn("/cep-1a!/cep-1b!/") == "1a!"