code: def test_pickling_index():
      # normal index
      i = toindex([1, 2, 3])
      i.tousertensor()
      i.todgltensor()  # construct a dgl tensor which is unpicklable
      i2 = _reconstruct_pickle(i)
      _assert_is_identical_index(i, i2)
  
      # slice index
      i = toindex(slice(5, 10))
      i2 = _reconstruct_pickle(i)
      _assert_is_identical_index(i, i2)
  
imports: import io
  import pickle
  import unittest
  import backend
  import dgl
  import dgl.function
  import networkx
  import pytest
  import scipy.sparse
  from dgl.graph_index import create_graph_index
  from dgl.utils import toindex
  from utils import assert_is_identical, assert_is_identical_hetero, check_graph_equal, get_cases, parametrize_idtype
label_desc: Use image node_id 6 for calling a global function with example usage: test_pickling_index() without return types