code: def setUp(self):
      self.g1 = Graph.Tree(5, 2, "undirected")
      self.g2 = Graph.Tree(10, 2, "undirected")
  
imports: import unittest
  from igraph import Graph
  from .utils import temporary_file
label_desc: Use image node_id 1 for calling the IndependentVertexSetTests obj's underlying member method code with example usage: obj.setUp() without return types