def METHOD_NAME():
    frr = MagicMock()
    c = ConfigMgr(frr)
    c.restart_peer_groups(["pg_1", "pg_2"])
    assert c.peer_groups_to_restart == ["pg_1", "pg_2"]
    c.restart_peer_groups(["pg_3", "pg_4"])
    assert c.peer_groups_to_restart == ["pg_1", "pg_2", "pg_3", "pg_4"]