code: def test_widget_client_np_date(self, rename_libraries):
      import perspective
  
      assert perspective.is_libpsp() is False
      data = {
          "a": np.array(
              [date(2020, i, 1) for i in range(1, 13)],
              dtype="datetime64[D]",
          )
      }
      widget = perspective.PerspectiveWidget(data)
      assert hasattr(widget, "table") is False
      assert widget._data == {
          "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 5 for calling the TestClient obj's underlying member method code with example usage: obj.test_widget_client_np_date(rename_libraries) without return types