code: def all_selectors(Class, fn):
          
          selectors = []
          cssparser = cssutils.CSSParser(validate=False)
          css = cssparser.parseFile(fn)
          for rule in [r for r in css.cssRules if type(r)==cssutils.css.CSSStyleRule]:
              selectors += [sel.selectorText for sel in rule.selectorList]
          selectors = sorted(list(set(selectors)))
          return selectors
docs: return a sorted list of selectors that occur in the stylesheet