code: def test_viewer_load_data(self):
      viewer = PerspectiveViewer()
      viewer.load({"a": [1, 2, 3]})
      assert viewer.columns == ["a"]
  
imports: import numpy
  import pandas
  from perspective import PerspectiveViewer, Table
label_desc: Use image node_id 4 for calling the TestViewer obj's underlying member method code with example usage: obj.test_viewer_load_data() without return types