def add_error(self, error):
        """
        In the case where a list/tuple is passed in this just extends the list
        rather than having nested lists.

        Otherwise, the value is appended.
        """
        if is_non_string_iterable(error) and not isinstance(error, collections.Mapping):
            for value in error:
                self.add_error(value)
        else:
            self.append(error)
In the case where a list/tuple is passed in this just extends the list
        rather than having nested lists.

        Otherwise, the value is appended.