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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_missing_placeholders(self):
 """ Add missing placeholders from templates. Return `True` if any missing placeholders were created. """

        content_type = ContentType.objects.get_for_model(self)
        result = False
        if self.layout:
            for data in self.layout.get_placeholder_data():
                placeholder, created = Placeholder.objects.update_or_create(
                    parent_type=content_type,
                    parent_id=self.pk,
                    slot=data.slot,
                    defaults=dict(
                        role=data.role,
                        title=data.title,
                    ))
                result = result or created
        return result