We should not use mutable objects as default arguments in python functions/methods, so I fixed it in the prototype class.

Before the change:
Every time we called the__deepcopy__ method (actually called by python when you use copy.deepcopy) without the memo argument, the same dict instance was being used. This happens because default arguments are instantiated atload-module time. Leads to dangerous behaviour: if you update the dict in some method-call, you will use the same updated dict in another calls.

Now:
The memo dict is created in every call without the memo argument.

ps: no changes to Output.txt are required