def add(self, elem, replace=False):
        """Add a requirement.

        :param elem: a string or :class:`Requirement` instance.
        :param replace: if `True`, packages in the set with the same name will
            be removed first.
        """
        if isinstance(elem, text_type):
            elem = Requirement.coerce(elem)
        if replace and elem in self:
            self.remove(elem)
        super(Requirements, self).add(elem)
def _load_from_file(self, fn):
        self._filename = fn
        with open(fn, "r") as f:
            try:
                replay_data = json.load(f)
            except json.decoder.JSONDecodeError as e:
                raise TransactionReplayError(fn, str(e) + ".")

        try:
            self._load_from_data(replay_data)
        except TransactionError as e:
            raise TransactionReplayError(fn, e)