code: def test_is_not_tree(self):
      assert not nx.is_tree(self.N4)
      assert not nx.is_tree(self.N5)
      assert not nx.is_tree(self.N6)
  
imports: import pytest
  import networkx
label_desc: Use image node_id 7 for calling the TestTreeRecognition obj's underlying member method code with example usage: obj.test_is_not_tree() without return types