'Constructs a relative path from a given prefix within the container.
URLs and paths starting with \'/\' are not modified.
:param prefix: The prefix for the container listing.'

def _build_css_path(self, prefix=''):

    if self._listings_css.startswith(('/', 'http://', 'https://')):
        css_path = quote(self._listings_css, ':/')
    else:
        css_path = (('../' * prefix.count('/')) + quote(self._listings_css))
    return css_path
