def prextend(self, var, values, create=False):
        if create:
            cur = self.get(var, [])
        else:
            cur = self[var]
        self[var] = values + cur
Clear any messages out of the messages framework for the authenticated
dataset/ETHPy150Open cournape/Bento/bento/private/_yaku/yaku/environment.py/Environment.prextend--crossover with--dataset/ETHPy150Open mozilla/addons-server/src/olympia/amo/utils.py/clear_messages