@classmethod
def merge_stylesheets(Class, fn, *cssfns):
    """merge the given CSS files, in order, into a single stylesheet. First listed takes priority.
        """
    stylesheet = Class(fn=fn)
    for cssfn in cssfns:
        css = Class(fn=cssfn)
        for sel in sorted(css.styles.keys()):
            if sel not in stylesheet.styles:
                stylesheet.styles[sel] = css.styles[sel]
            else:
                for prop in [prop for prop in css.styles[sel] if prop not in
                    stylesheet.styles[sel]]:
                    stylesheet.styles[sel][prop] = css.styles[sel][prop]
    return stylesheet
