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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 _get_model_reference(self, model_id):
 """Constructs a ModelReference. Args: model_id (str):
 the ID of the model. Returns: google.cloud.bigquery.model.ModelReference: A ModelReference for a model in this dataset. """

    return ModelReference.from_api_repr(
        {"projectId": self.project, "datasetId": self.dataset_id, "modelId": model_id}
    )