code: def test_viewer_delete(self):
      table = Table({"a": [1, 2, 3]})
      viewer = PerspectiveViewer(
          plugin="X Bar", filter=[["a", "==", 2]]
      )
      viewer.load(table)
      assert viewer.filter == [["a", "==", 2]]
      viewer.delete()
      assert viewer.table_name is None
      assert viewer.table is None
  
imports: import numpy
  import pandas
  from perspective import PerspectiveViewer, Table
label_desc: Use image node_id 21 for calling the TestViewer obj's underlying member method code with example usage: obj.test_viewer_delete() without return types