def wb_LR_pair(func_LR, arg_LR=None, after=True):
    """
    Get wb_command left- and right- arguments
    :param func_LR: Function which accepts 'L' or 'R' and returns a filepath
    :param arg_LR: String naming the left- or right- argument
    :param after: True if arg_LR goes after the word 'left'/'right'; else False
    :return: List with 4 elements, arg name and then value for left then right
    """
    arg_LR = '-' + arg_LR if arg_LR else ''
    arg_fmt = '-{}' + arg_LR if after else arg_LR + '-{}'
    return [arg_fmt.format('left'), func_LR('L'),
            arg_fmt.format('right'), func_LR('R')]