code: def test_concatenate1(n=10):
      x1 = nr.randn(n, 2)
      x2 = nr.randn(n, 2)
      G1 = knn(x1, 5)
      G2 = knn(x2, 5)
      G = concatenate_graphs(G1, G2)
      assert G.cc().max() > 0
  
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 38 for calling a global function with example usage: test_concatenate1(n) without return types