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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_untagged(self, *responses: 'Response') -> None: """Add an untagged response. These responses are shown before the parent response. Args: responses: The untagged responses to add. """

        for resp in responses:
            try:
                merge_key = resp.merge_key
            except TypeError:
                self._untagged.append(resp)
            else:
                key = (type(resp), merge_key)
                try:
                    untagged_idx = self._mergeable[key]
                except KeyError:
                    untagged_idx = len(self._untagged)
                    self._mergeable[key] = untagged_idx
                    self._untagged.append(resp)
                else:
                    merged = self._untagged[untagged_idx].merge(resp)
                    self._untagged[untagged_idx] = merged
        self._raw = None