Allow `DatasetListItem` in `Client.delete_dataset` types

[tswast]

https://app.circleci.com/pipelines/github/tswast/python-bigquery-pandas/217/workflows/38a35d17-9e68-48b3-b17a-b683e4ab5a52/jobs/1308

I expected this code to work:

    @pytest.fixture(scope="session", autouse=True)
    def cleanup_datasets(bigquery_client: bigquery.Client):
        for dataset in bigquery_client.list_datasets():
            if prefixer.should_cleanup(dataset.dataset_id):
                bigquery_client.delete_dataset(
>                   dataset, delete_contents=True, not_found_ok=True
                )

But I get

if not isinstance(dataset, (Dataset, DatasetReference)):
>           raise TypeError("dataset must be a Dataset or a DatasetReference")
E           TypeError: dataset must be a Dataset or a DatasetReference

/opt/conda/envs/test-environment/lib/python3.7/site-packages/google/cloud/bigquery/client.py:740: TypeError

Similarly, we should check delete_table. I think it accepts TableListItem, but this is not reflected in the type annotations.

[tswast]

@steffnay This might be a good one to take on if you're looking for issues to get warmed up on the Python client.

[steffnay]

@tswast could you please clarify for me whether this TypeError was not fixed by #597 or if the issue here is that the type needs to be updated here?

[tswast]

Oops.

https://github.com/googleapis/python-bigquery-pandas/blob/6ae6629db0aec48ecd37a96a75f950fea63405c7/testing/constraints-3.7.txt#L12

This test suite was running with an older version of the google-cloud-bigquery library.

Sorry for the noise.

[tswast]

python-bigquery/google/cloud/bigquery/client.py

Line 1528 in b15b612

dataset: Union[Dataset, DatasetReference, str],

does still need to be updated though, yes.