def METHOD_NAME(v, target_visibility_unit='kilometers'):
    """
    Converts visibility distance (in meters) to kilometers or miles
    Defaults to kilometer conversion
    :param distance: the value of visibility_distance
    :type distance: int
    :param target_visibility_unit: the unit of conversion
    :type target_visibility_unit: str
    :returns: a converted value for visibility_distance (float)
    """
    if v is None:
        return v
    if target_visibility_unit == 'kilometers':
        const = KMS_FOR_ONE_METER
    elif target_visibility_unit == 'miles':
        const = MILE_FOR_ONE_METER
    else:
        raise ValueError('Invalid value for target visibility distance unit')
    return round(v * const, ROUNDED_TO)