sqlalchemy engine seems to caching metadata causing inconsistency

Running the following in test_timeseries_mapper.py will raise an error due to inconsistency between the ingested table and the Metadata() object.

def test__one_week_per_month_by_hour(iter_engines: Engine):
    run_test(iter_engines, one_week=True, tzinfo=None) # this has no time_zone
    run_test(iter_engines, one_week=True, tzinfo=ZoneInfo("US/Eastern")) # this expects time_zone

The metadata object seems to be retaining remnant of the first run_test, which does not have a time_zone column, whereas the second test does.

Confirmed by running the pytest as a regular function that it is not a pytest issue.

The current workaround is to parametrize the pytest on tzinfo or keep each run_test as separate function so that the engine is created new each time.

Start by running the reproducer in test_timeseries_mapper.py as a regular function and under pytest, focusing on how the engine and Metadata() are reused across the two run_test calls. Done means consecutive calls with and without tzinfo no longer retain inconsistent table metadata, while the relevant test passes without requiring separate functions or a new engine.