def change_deco(name, deco, placeholder='    #'):
    with open(name + '.py', 'r') as file:
        lines = file.readlines()
    for idx, string in enumerate(lines):
        if placeholder in string and repr(placeholder) not in string:
            lines[idx] = f'    @{deco}\r\n'
    exec(''.join(lines))
    return locals()[name]