from copy import deepcopy


class Storage:
    def __init__(self):
        self._dict = dict()

    def __getitem__(self, item):
        return self._dict[item]

    def edit(self):
        return self.ContextManager(self)

    class ContextManager:
        def __init__(self, storage):
            self.storage = storage
            self.copy_dict = deepcopy(storage._dict)

        def __enter__(self):
            return self

        def __exit__(self, exc_type, exc_val, exc_tb):
            if exc_type:
                # raise
                return True

            self.storage._dict = self.copy_dict
            return True

        def __getitem__(self, key):
            return self.copy_dict[key]

        def __setitem__(self, key, value):
            self.copy_dict[key] = value

        def __delitem__(self, key):
            del self.copy_dict[key]