code: def test_make_complete_graph(num_vertices, expected_grid, backend):
      V = num_vertices
      K = V * (V - 1) // 2
      expected_grid = torch.tensor(
          expected_grid, dtype=torch.long
      ).reshape(2, K)
  
      grid = make_complete_graph(V, backend=backend)
      assert_equal(grid, expected_grid)
  
file_path: pyro/tests/distributions/test_spanning_tree.py
imports: import logging
  import os
  from collections import Counter
  import pytest
  import torch
  import pyro
  from pyro.distributions.spanning_tree import NUM_SPANNING_TREES, SpanningTree, find_best_tree, make_complete_graph, sample_tree
  from tests.common import assert_equal, xfail_if_not_implemented
label_desc: Use image node_id 1 for calling a global function with example usage: test_make_complete_graph(num_vertices, expected_grid, backend) without return types