code: def _test_map_to_subgraph():
      g = dgl.graph([])
      g.add_nodes(10)
      g.add_edges(F.arange(0, 9), F.arange(1, 10))
      h = g.subgraph([0, 1, 2, 5, 8])
      v = h.map_to_subgraph_nid([0, 8, 2])
      assert np.array_equal(F.asnumpy(v), np.array([0, 4, 2]))
  
imports: import unittest
  import backend
  import dgl
  import networkx
  import numpy
  import pytest
  import scipy.sparse
  from utils import parametrize_idtype
label_desc: Use image node_id 4 for calling a global function with example usage: _test_map_to_subgraph() without return types