expand any variables in the action to_from/cc_from fields.

def expand_variables(self, message):
        """expand any variables in the action to_from/cc_from fields.
        """
        p = copy.deepcopy(self.data)
        if 'to_from' in self.data:
            to_from = self.data['to_from'].copy()
            to_from['url'] = to_from['url'].format(**message)
            if 'expr' in to_from:
                to_from['expr'] = to_from['expr'].format(**message)
            p.setdefault('to', []).extend(ValuesFrom(to_from, self.manager).get_values())
        if 'cc_from' in self.data:
            cc_from = self.data['cc_from'].copy()
            cc_from['url'] = cc_from['url'].format(**message)
            if 'expr' in cc_from:
                cc_from['expr'] = cc_from['expr'].format(**message)
            p.setdefault('cc', []).extend(ValuesFrom(cc_from, self.manager).get_values())
        return p