def METHOD_NAME(opts):
    args = (
        opts.filename_in,
        opts.calculator_in,
        opts.filename_out,
        opts.calculator_out,
    )
    try:
        _is_file_None(args[0], "input")
        _infile_exist(args[0])
        _is_file_None(args[2], "output")
        _outfile_exist(args[2])
        _is_calc_None(args[1], "input")
        _calc_check(args[1])
        _is_calc_None(args[3], "output")
        _calc_check(args[3])
    except (RuntimeError, FileNotFoundError) as err:
        print("ERROR: %s" % err)
    convert_crystal_structure(*args)