code: def testBug128(self):
      y = [1, 4, 9]
      g = Graph(n=len(y), directed=True, vertex_attrs={"y": y})
      self.assertEqual(3, g.vcount())
      g.add_vertices(1)
      # Bug #128 would prevent us from reaching the next statement
      # because an exception would have been thrown here
      self.assertEqual(4, g.vcount())
  
imports: import unittest
  from igraph import Graph
label_desc: Use image node_id 1 for calling the UnicodeTests obj's underlying member method code with example usage: obj.testBug128() without return types