def METHOD_NAME():
    """Handle mandatory and optional command line arguments"""
    if len(sys.argv) not in range(2, 5):
        fail(f"Usage: {sys.argv[0]} <FRITZ!Box XML> [<Baresip contacts>] "
             "[<FRITZ!Box IP>]")
    return sys.argv[1], \
           sys.argv[2] if len(sys.argv) >= 3 else None, \
           f"@{sys.argv[3]}" if len(sys.argv) == 4 else "@fritz.box"