code: def test_batch_no_edge(idtype):
      g1 = dgl.graph(([], [])).astype(idtype).to(F.ctx())
      g1.add_nodes(6)
      g1.add_edges([4, 4, 2, 2, 0], [5, 3, 3, 1, 1])
      g2 = dgl.graph(([], [])).astype(idtype).to(F.ctx())
      g2.add_nodes(6)
      g2.add_edges([0, 1, 2, 5, 4, 5], [1, 2, 3, 4, 3, 0])
      g3 = dgl.graph(([], [])).astype(idtype).to(F.ctx())
      g3.add_nodes(1)  # no edges
      g = dgl.batch([g1, g3, g2])
  
file_path: dgl/tests/python/common/test_batch-graph.py
imports: import unittest
  import backend
  import dgl
  import numpy
  from utils import parametrize_idtype
label_desc: Use image node_id 10 for calling a global function with example usage: test_batch_no_edge(idtype) without return types