code: def test_widget_no_data_with_index(self):
      # should fail
      with raises(PerspectiveError):
          PerspectiveWidget(None, index="a")
  
imports: from datetime import date, datetime
  from functools import partial
  from types import MethodType
  import numpy
  from perspective import PerspectiveError, PerspectiveWidget, Table
  from pytest import raises
label_desc: Use image node_id 7 for calling the TestWidget obj's underlying member method code with example usage: obj.test_widget_no_data_with_index() without return types