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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 _save(self):
 """Save the sub-resource within the parent resource"""

        yield self.validate()

        try:
            self._parent = yield self.parent_resource.get(self.parent_id)
        except couch.NotFound:
            msg = '{}_id {} not found'.format(
                self.parent_resource.resource_type,
                self.parent_id)
            raise exceptions.ValidationError(msg)

        yield self._parent.save_subresource(self)