code: def test_widget_client_df_date_object(self, rename_libraries):
      import perspective
  
      assert perspective.is_libpsp() is False
      data = pd.DataFrame(
          {"a": [date(2020, i, 1) for i in range(1, 13)]},
          dtype="object",
      )
      widget = perspective.PerspectiveWidget(data)
      assert hasattr(widget, "table") is False
      assert widget._data == {
          "index": [i for i in range(12)],
          "a": ["2020-{:02d}-01".format(i) for i in range(1, 13)],
      }
  
imports: import os
  import pytest
  import sys
  import numpy
  import pandas
  from datetime import date, datetime
  from functools import partial
  from types import MethodType
label_desc: Use image node_id 8 for calling the TestClient obj's underlying member method code with example usage: obj.test_widget_client_df_date_object(rename_libraries) without return types