Final nits

evalml/pipelines/utils.py

@@ -1489,7 +1489,7 @@ def stack_X(X, series_id_name, time_index, starting_index=None, series_id_values
         time_index (str): The name of the time index column.
         starting_index (int): The starting index to use for the stacked DataFrame. If None, the starting index
             will match that of the input data. Defaults to None.
-        series_id_values (set): The unique values of a series ID, used to generate the index. If None, values will
+        series_id_values (set, list): The unique values of a series ID, used to generate the index. If None, values will
             be generated from X column values. Required if X only has time index values and no exogenous values.
             Defaults to None.
 
@@ -1508,7 +1508,7 @@ def stack_X(X, series_id_name, time_index, starting_index=None, series_id_values
 
     if len(series_ids) == 0:
         raise ValueError(
-            "Series ID values needs to be passed in X column values or as a set with the `series_id_values` parameter.",
+            "Series ID values need to be passed in X column values or as a set with the `series_id_values` parameter.",
         )
 
     time_index_col = X[time_index].repeat(len(series_ids)).reset_index(drop=True)

evalml/tests/pipeline_tests/test_pipeline_utils.py

@@ -1472,11 +1472,13 @@ def test_stack_data_noop():
     pd.testing.assert_series_equal(stack_data(series_y), series_y)
 
 
+@pytest.mark.parametrize("series_id_values_type", [set, list])
 @pytest.mark.parametrize("no_features", [True, False])
 @pytest.mark.parametrize("starting_index", [None, 1, 132])
 def test_stack_X(
     starting_index,
     no_features,
+    series_id_values_type,
     multiseries_ts_data_stacked,
     multiseries_ts_data_unstacked,
 ):
@@ -1487,13 +1489,13 @@ def test_stack_X(
         X_expected.index = X_expected.index + starting_index
 
     if no_features:
-        series_id_values = set(str(i) for i in range(0, 5))
+        series_id_values = series_id_values_type(str(i) for i in range(0, 5))
         X = pd.DataFrame(X["date"])
         X_expected = X_expected[["date", "series_id"]]
 
         with pytest.raises(
             ValueError,
-            match="Series ID values needs to be passed in X column values or as a set with the `series_id_values` parameter.",
+            match="Series ID values need to be passed in X column values or as a set with the `series_id_values` parameter.",
         ):
             stack_X(X, "series_id", "date", starting_index=starting_index)