code: def testCombinationNonexistentAttribute(self):
      g = self.g
      g.simplify(combine_edges={"nonexistent": max})
      self.assertTrue(g.edge_attributes() == [])
  
imports: import unittest
  from igraph import Graph
label_desc: Use image node_id 18 for calling the AttributeCombinationTests obj's underlying member method code with example usage: obj.testCombinationNonexistentAttribute() without return types