code: def test_empty_graph(total_num_nodes):
      csc_indptr = torch.zeros((total_num_nodes + 1,), dtype=int)
      indices = torch.tensor([])
      graph = gb.fused_csc_sampling_graph(csc_indptr, indices)
      assert graph.total_num_edges == 0
      assert graph.total_num_nodes == total_num_nodes
      assert torch.equal(graph.csc_indptr, csc_indptr)
      assert torch.equal(graph.indices, indices)
  
imports: import os
  import pickle
  import re
  import tempfile
  import unittest
  import backend
  import dgl
  import dgl.graphbolt
  import pytest
  import torch
  import torch.multiprocessing
  from dgl.graphbolt.base import etype_str_to_tuple
  from scipy import sparse
  from ..None import gb_test_utils
label_desc: Use image node_id 1 for calling a global function with example usage: test_empty_graph(total_num_nodes) without return types