Update automl_tables_predict.py with batch_predict_bq sample [(#4142)](GoogleCloudPlatform/python-docs-samples#4142)

Added a new method `batch_predict_bq` demonstrating running batch_prediction using BigQuery.
Added notes in comments about asynchronicity for `batch_predict` method.

The region `automl_tables_batch_predict_bq` will be used on cloud.google.com (currently both sections for GCS and BigQuery use the same sample code which is incorrect).

Fixes #4141

Note: It's a good idea to open an issue first for discussion.

- [x] Please **merge** this PR for me once it is approved.

Author: evil-shrike

samples/tables/automl_tables_predict.py

@@ -81,6 +81,49 @@ def predict(
     # [END automl_tables_predict]
 
 
+def batch_predict_bq(
+    project_id,
+    compute_region,
+    model_display_name,
+    bq_input_uri,
+    bq_output_uri,
+):
+    """Make a batch of predictions."""
+    # [START automl_tables_batch_predict_bq]
+    # TODO(developer): Uncomment and set the following variables
+    # project_id = 'PROJECT_ID_HERE'
+    # compute_region = 'COMPUTE_REGION_HERE'
+    # model_display_name = 'MODEL_DISPLAY_NAME_HERE'
+    # bq_input_uri = 'bq://my-project.my-dataset.my-table'
+    # bq_output_uri = 'bq://my-project'
+
+    from google.cloud import automl_v1beta1 as automl
+
+    client = automl.TablesClient(project=project_id, region=compute_region)
+
+    # Query model
+    response = client.batch_predict(bigquery_input_uri=bq_input_uri,
+                                    bigquery_output_uri=bq_output_uri,
+                                    model_display_name=model_display_name)
+    print("Making batch prediction... ")
+    # `response` is a async operation descriptor,
+    # you can register a callback for the operation to complete via `add_done_callback`:
+    # def callback(operation_future):
+    #   result = operation_future.result()
+    # response.add_done_callback(callback)
+    #
+    # or block the thread polling for the operation's results:
+    response.result()
+    # AutoML puts predictions in a newly generated dataset with a name by a mask "prediction_" + model_id + "_" + timestamp
+    # here's how to get the dataset name:
+    dataset_name = response.metadata.batch_predict_details.output_info.bigquery_output_dataset
+
+    print("Batch prediction complete.\nResults are in '{}' dataset.\n{}".format(
+        dataset_name, response.metadata))
+
+    # [END automl_tables_batch_predict_bq]
+
+
 def batch_predict(
     project_id,
     compute_region,
@@ -108,7 +151,15 @@ def batch_predict(
         model_display_name=model_display_name,
     )
     print("Making batch prediction... ")
+    # `response` is a async operation descriptor,
+    # you can register a callback for the operation to complete via `add_done_callback`:
+    # def callback(operation_future):
+    #   result = operation_future.result()
+    # response.add_done_callback(callback)
+    #
+    # or block the thread polling for the operation's results:
     response.result()
+
     print("Batch prediction complete.\n{}".format(response.metadata))
 
     # [END automl_tables_batch_predict]

samples/tables/batch_predict_test.py

@@ -30,6 +30,8 @@
 STATIC_MODEL = model_test.STATIC_MODEL
 GCS_INPUT = "gs://{}-automl-tables-test/bank-marketing.csv".format(PROJECT)
 GCS_OUTPUT = "gs://{}-automl-tables-test/TABLE_TEST_OUTPUT/".format(PROJECT)
+BQ_INPUT = "bq://{}.automl_test.bank_marketing".format(PROJECT)
+BQ_OUTPUT = "bq://{}".format(PROJECT)
 
 
 @pytest.mark.slow
@@ -42,6 +44,16 @@ def test_batch_predict(capsys):
     assert "Batch prediction complete" in out
 
 
+@pytest.mark.slow
+def test_batch_predict_bq(capsys):
+    ensure_model_online()
+    automl_tables_predict.batch_predict_bq(
+        PROJECT, REGION, STATIC_MODEL, BQ_INPUT, BQ_OUTPUT
+    )
+    out, _ = capsys.readouterr()
+    assert "Batch prediction complete" in out
+
+
 def ensure_model_online():
     model = model_test.ensure_model_ready()
     if model.deployment_state != enums.Model.DeploymentState.DEPLOYED: