docs: add snippet to see the ARIMA coefficients in the Forecast a single time series with a univariate model tutorial (#1268)

* merge main * details * Update samples/snippets/create_single_timeseries_forecasting_model_test.py Co-authored-by: Tim Sweña (Swast) <swast@google.com> * fix * edit --------- Co-authored-by: Tim Sweña (Swast) <swast@google.com>

Author: rey-esp

samples/snippets/create_single_timeseries_forecasting_model_test.py

@@ -64,6 +64,17 @@ def test_create_single_timeseries() -> None:
 
  model.fit(X, y)
  # [END bigquery_dataframes_single_timeseries_forecasting_model_tutorial_create]
+
+ # [START bigquery_dataframes_single_timeseries_forecasting_model_tutorial_evaluate]
+ coef = model.coef_
+ print(coef.peek())
+
+ # Expected output:
+ # ar_coefficients ma_coefficients intercept_or_drift
+ # 0 [0.40944762] [-0.81168198] 0.0
+
+ # [END bigquery_dataframes_single_timeseries_forecasting_model_tutorial_evaluate]
+ assert coef is not None
  assert model is not None
  assert parsed_date is not None
  assert total_visits is not None