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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 retrieve(self, request, _id):
 """ Returns the document containing the given _id or 404 """

        _id = deserialize(_id)

        retrieved = self.collection.find_one({'_id': _id})
        if retrieved:
            return Response(serialize(retrieved))
        else:
            return Response(
                response=serialize(
                    DocumentNotFoundError(self.collection.__name__, _id)
                ),
                status=400
            )