def _keep_alive(x, memo):
    try:
        memo[id(memo)].append(x)
    except KeyError:
        # aha, this is the first one :-)
        memo[id(memo)]=[x]
Keeps a reference to the object x in the memo.
dataset/ETHPy150Open amrdraz/kodr/app/brython/www/src/Lib/copy.py/_keep_alive