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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def parse_css(self, css):
 """ Parse a css style sheet into the CSS object. For the moment this will only work for very simple css documents. It works by using regular expression matching css syntax. This is not bullet proof. """

        rulesets = self.ruleset_re.findall(css)
        for (selector, declarations) in rulesets:
            rule = Rule(self.parse_selector(selector))
            rule.properties = self.parse_declarations(declarations)
            self.rules.append(rule)