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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 delete_orphan_translations(condition=None):
 		""" 		Delete orphan translations. 		This method needs refactoring to be improve its performance. 		"""

		if condition is None:
			condition = {}
		# TODO: optimize using one SQL sentence
		translations = FieldTranslation.objects.all()
		for translation in translations:
			translation._load_source_model()
			condition["id"] = translation.object_id
			if not translation.source_model.objects.filter(**condition).exists():
				translation.delete()