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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 limit_roles(self):
 """ Limit the roles being scanned. """

        new_roles = {}
        roles = self.options.limit.split(",")

        for key, value in self.roles.iteritems():
            for role in roles:
                role = role.strip()
                if key == role:
                    new_roles[key] = value

        self.roles = new_roles