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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 _create_epoch_data(self, streams: Optional[Iterable[str]]=None) -> EpochData: """Create empty epoch data double dict."""

        if streams is None:
            streams = [self._train_stream_name] + self._extra_streams
        return OrderedDict([(stream_name, OrderedDict()) for stream_name in streams])