def _test():
    """
       >>> x = css(color='red', background='blue')
       >>> x
       color:red;background:blue
       >>> x.border = 'none'
       >>> y = css(background='blue', color='red')
       >>> y.border = 'none'
       >>> x == y
       True
       >>> a = css()
        >>> a['font-weight'] = 'bold'
        >>> a
        font-weight:bold
        >>> a.text_align = 'right'
        >>> a
        font-weight:bold;text-align:right
    """
    import doctest
    doctest.testmod()
