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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_dataset(self, dataset_ref, retry=DEFAULT_RETRY):
 """Fetch the dataset referenced by ``dataset_ref`` Args: dataset_ref (Union[ \ :class:`~google.cloud.bigquery.dataset.DatasetReference`, \ str, \ ]):
 A reference to the dataset to fetch from the BigQuery API. If a string is passed in, this method attempts to create a dataset reference from a string using :func:`~google.cloud.bigquery.dataset.DatasetReference.from_string`. retry (:class:`google.api_core.retry.Retry`):
 (Optional) How to retry the RPC. Returns: google.cloud.bigquery.dataset.Dataset: A ``Dataset`` instance. """

        if isinstance(dataset_ref, str):
            dataset_ref = DatasetReference.from_string(
                dataset_ref, default_project=self.project
            )

        api_response = self._call_api(retry, method="GET", path=dataset_ref.path)
        return Dataset.from_api_repr(api_response)