code: def testEmptySequence(self):
      empty_vs = self.g.vs.select(None)
      self.assertTrue(len(empty_vs) == 0)
      self.assertRaises(IndexError, empty_vs.__getitem__, 0)
      self.assertRaises(KeyError, empty_vs.__getitem__, "nonexistent")
      self.assertTrue(empty_vs["test"] == [])
      empty_vs = self.g.vs[[]]
      self.assertTrue(len(empty_vs) == 0)
      empty_vs = self.g.vs[()]
      self.assertTrue(len(empty_vs) == 0)
  
imports: import unittest
  from igraph import Graph, Vertex, VertexSeq
  from .utils import is_pypy
label_desc: Use image node_id 8 for calling the VertexSeqTests obj's underlying member method code with example usage: obj.testEmptySequence() without return types