fix(automl): fix uploading pandas dataframe to AutoML Tables (#9647)

pandas.dataframe.to_csv() by default exports data index as an column
with empty column name. This causes uploading the export csv file to
fail because AutoML Tables does not allow empty column names. Given
that the data index is not useful for training the model. This PR
fixes the problem by setting the index argument to false so that the
index is not exported.

automl/google/cloud/automl_v1beta1/tables/gcs_client.py

@@ -132,7 +132,12 @@ def upload_pandas_dataframe(self, dataframe, uploaded_csv_name=None):
             uploaded_csv_name = "automl-tables-dataframe-{}.csv".format(
                 int(time.time())
             )
-        csv_string = dataframe.to_csv()
+
+        # Setting index to False to ignore exporting the data index:
+        # 1. The resulting column name for the index column is empty, AutoML
+        # Tables does not allow empty column name
+        # 2. The index is not an useful training information
+        csv_string = dataframe.to_csv(index=False)
 
         bucket = self.client.get_bucket(self.bucket_name)
         blob = bucket.blob(uploaded_csv_name)

automl/tests/unit/gapic/v1beta1/test_gcs_client_v1beta1.py

@@ -139,7 +139,7 @@ def test_upload_pandas_dataframe(self):
 
         gcs_client.client.get_bucket.assert_called_with("my-bucket")
         mock_bucket.blob.assert_called_with("my-file.csv")
-        mock_blob.upload_from_string.assert_called_with(",col1,col2\n0,1,3\n1,2,4\n")
+        mock_blob.upload_from_string.assert_called_with("col1,col2\n1,3\n2,4\n")
         assert gcs_uri == "gs://my-bucket/my-file.csv"
 
     def test_upload_pandas_dataframe_no_csv_name(self):
@@ -156,7 +156,7 @@ def test_upload_pandas_dataframe_no_csv_name(self):
 
         gcs_client.client.get_bucket.assert_called_with("my-bucket")
         mock_bucket.blob.assert_called_with(generated_csv_name)
-        mock_blob.upload_from_string.assert_called_with(",col1,col2\n0,1,3\n1,2,4\n")
+        mock_blob.upload_from_string.assert_called_with("col1,col2\n1,3\n2,4\n")
         assert re.match("^gs://my-bucket/automl-tables-dataframe-[0-9]*.csv$", gcs_uri)
 
     def test_upload_pandas_dataframe_not_type_dataframe(self):