code: def test_widget_load_group_by(self, superstore):
      df_pivoted = superstore.set_index(["Country", "Region"])
      widget = PerspectiveWidget(df_pivoted)
      assert widget.group_by == ["Country", "Region"]
      assert widget.split_by == []
      assert sorted(widget.columns) == sorted(
          [
              "index",
              "Category",
              "Country",
              "City",
              "Customer ID",
              "Discount",
              "Order Date",
              "Order ID",
              "Postal Code",
              "Product ID",
              "Profit",
              "Quantity",
              "Region",
              "Row ID",
              "Sales",
              "Segment",
              "Ship Date",
              "Ship Mode",
              "State",
              "Sub-Category",
          ]
      )
      assert widget.table.size() == 100
      view = widget.table.view()
      assert view.num_rows() == len(superstore)
      assert view.num_columns() == len(superstore.columns) + 1
  
file_path: perspective/python/perspective/perspective/tests/widget/test_widget_pandas.py
imports: from datetime import date
  import pandas
  import numpy
  from perspective import Table, PerspectiveWidget
label_desc: Use image node_id 6 for calling the TestWidgetPandas obj's underlying member method code with example usage: obj.test_widget_load_group_by(superstore) without return types