def aggregate_events(events: pd.DataFrame) -> pd.DataFrame:
    """Returns a table of items and their aggregated impressions and clicks."""
    events_agg = events.pivot_table(index=['item'], columns=['event_type'], values=['request_id'],
                                    aggfunc='count', fill_value=0)
    events_agg.columns = events_agg.columns.droplevel()
    events_agg = events_agg.reset_index()

    # Clear index name
    events_agg = events_agg.rename_axis(None, axis=1)

    return events_agg


# Unit test: Table level
def test_aggregate_events(events):
    result = aggregate_events(events)

    arr = [['i1', 0, 5],
           ['i2', 1, 5],
           ['i3', 1, 5],
           ['i4', 0, 5]]
    cols = ['item', 'click', 'impress']
    expected = pd.DataFrame(arr, columns=cols)

    pd.testing.assert_frame_equal(result, expected)