updates an import step and restores gc import

Author: chalmerlowe

tests/unit/test__pandas_helpers.py

@@ -16,6 +16,7 @@
 import datetime
 import decimal
 import functools
+import gc
 import operator
 import queue
 from typing import Union
@@ -1886,7 +1887,6 @@ def fake_download_stream(
     assert queue_used.maxsize == expected_maxsize
 
 
-'''
 @pytest.mark.skipif(isinstance(pyarrow, mock.Mock), reason="Requires `pyarrow`")
 def test__download_table_bqstorage_shuts_down_workers(
     monkeypatch,
@@ -1897,6 +1897,7 @@ def test__download_table_bqstorage_shuts_down_workers(
     Make sure that when the top-level iterator goes out of scope (is deleted),
     the child threads are also stopped.
     """
+    pytest.importorskip("google.cloud.bigquery_storage_v1")
     from google.cloud.bigquery import dataset
     from google.cloud.bigquery import table
     import google.cloud.bigquery_storage_v1.reader
@@ -2013,7 +2014,6 @@ def test_download_arrow_row_iterator_unknown_field_type(module_under_test):
     col = result.columns[1]
     assert type(col) is pyarrow.lib.DoubleArray
     assert col.to_pylist() == [2.2, 22.22, 222.222]
-'''
 
 
 @pytest.mark.skipif(isinstance(pyarrow, mock.Mock), reason="Requires `pyarrow`")