Implements Nested CSS rules

def _nest_rules(self, rule, p_selectors, p_parents, p_children, scope, media, c_lineno, c_property, c_codestr):
        """
        Implements Nested CSS rules
        """
        if c_property == self.construct and rule[MEDIA] == media:
            rule[CODESTR] = c_codestr
            self.manage_children(
                rule, p_selectors, p_parents, p_children, scope, media)
        else:
            c_property = self.apply_vars(
                c_property, rule[CONTEXT], rule[OPTIONS], rule, True)

            c_selectors = self.normalize_selectors(c_property)
            c_selectors, _, c_parents = c_selectors.partition(' extends ')

            better_selectors = set()
            c_selectors = c_selectors.split(',')
            for c_selector in c_selectors:
                for p_selector in p_selectors:
                    if c_selector == self.construct:
                        better_selectors.add(p_selector)
                    elif '&' in c_selector:  # Parent References
                        better_selectors.add(
                            c_selector.replace('&', p_selector))
                    elif p_selector:
                        better_selectors.add(p_selector + ' ' + c_selector)
                    else:
                        better_selectors.add(c_selector)
            better_selectors = ','.join(sorted(better_selectors))

            if c_parents:
                parents = set(p.strip() for p in c_parents.split('&'))
                parents.discard('')
                if parents:
                    better_selectors += ' extends ' + '&'.join(sorted(parents))

            _rule = spawn_rule(rule, codestr=c_codestr, deps=set(), context=rule[CONTEXT].copy(), options=rule[OPTIONS].copy(), selectors=better_selectors, properties=[], final=False, media=media, lineno=c_lineno)

            p_children.appendleft(_rule)