<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def additions_version():
    '''
    Check VirtualBox Guest Additions version.

    CLI Example:

    .. code-block:: bash

        salt '*' vbox_guest.additions_version

    :return: version of VirtualBox Guest Additions or False if they are not installed
    '''
    try:
        d = _additions_dir()
    except EnvironmentError:
        return False
    if d and os.listdir(d):
        return re.sub(r'^{0}-'.format(_additions_dir_prefix), '',
                os.path.basename(d))
    return False