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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 _convert_trigger(self, trigger_def, parent):
 """Convert a TriggerDefinition into a stream, trigger pair."""


        if trigger_def.explicit_stream is None:
            stream = parent.resolve_identifier(trigger_def.named_event, DataStream)
            trigger = TrueTrigger()
        else:
            stream = trigger_def.explicit_stream
            trigger = trigger_def.explicit_trigger

        return (stream, trigger)