code: def test_concatenate3():
      """test the graph concatenation utlitity"""
      bg = basic_graph()
      cg = concatenate_graphs(bg, bg)
      valid = np.zeros(cg.V)
      valid[: bg.V] = 1
      sg = cg.subgraph(valid)
      assert_array_equal(sg.edges, bg.edges)
      assert_array_equal(sg.weights, bg.weights)
  
imports: import numpy
  import numpy.random
  from numpy.testing import assert_almost_equal, assert_array_almost_equal, assert_array_equal
  from ..graph import WeightedGraph, complete_graph, concatenate_graphs, eps_nn, knn, mst, wgraph_from_3d_grid, wgraph_from_adjacency, wgraph_from_coo_matrix
label_desc: Use image node_id 48 for calling a global function with example usage: test_concatenate3() without return types