def prepend(self, var, value, create=False):
        if create:
            cur = self.get(var, [])
        else:
            cur = self[var]
        self[var] = [value] + cur
Prepend a single item to the list.
dataset/ETHPy150Open cournape/Bento/bento/private/_yaku/yaku/environment.py/Environment.prepend