class_docstr: For testing of AttrTree
class_docstr_tok: ["For","testing","of","AttrTree"]
code: def test_number_getitem_key_error(self):
      with self.assertRaises(KeyError):
          self.tree["2"]
  
imports: import pytest
  from holoviews.core.element import AttrTree
  from holoviews.element.comparison import ComparisonTestCase
label_desc: Use image node_id 7 for calling the AttrTreeTest obj's underlying member method code with example usage: obj.test_number_getitem_key_error() without return types