code: def test_barbell_graph(self):
      # number of nodes = 2*m1 + m2 (2 m1-complete graphs + m2-path + 2 edges)
      # number of edges = 2*(nx.number_of_edges(m1-complete graph) + m2 + 1
      m1 = 3
      m2 = 5
      b = nx.barbell_graph(m1, m2)
      assert nx.number_of_nodes(b) == 2 * m1 + m2
      assert nx.number_of_edges(b) == m1 * (m1 - 1) + m2 + 1
  
      m1 = 4
      m2 = 10
      b = nx.barbell_graph(m1, m2)
      assert nx.number_of_nodes(b) == 2 * m1 + m2
      assert nx.number_of_edges(b) == m1 * (m1 - 1) + m2 + 1
  
      m1 = 3
      m2 = 20
      b = nx.barbell_graph(m1, m2)
      assert nx.number_of_nodes(b) == 2 * m1 + m2
      assert nx.number_of_edges(b) == m1 * (m1 - 1) + m2 + 1
  
      # Raise NetworkXError if m1<2
      m1 = 1
      m2 = 20
      pytest.raises(nx.NetworkXError, nx.barbell_graph, m1, m2)
  
      # Raise NetworkXError if m2<0
      m1 = 5
      m2 = -2
      pytest.raises(nx.NetworkXError, nx.barbell_graph, m1, m2)
  
      # nx.barbell_graph(2,m) = nx.path_graph(m+4)
      m1 = 2
      m2 = 5
      b = nx.barbell_graph(m1, m2)
      assert is_isomorphic(b, nx.path_graph(m2 + 4))
  
      m1 = 2
      m2 = 10
      b = nx.barbell_graph(m1, m2)
      assert is_isomorphic(b, nx.path_graph(m2 + 4))
  
      m1 = 2
      m2 = 20
      b = nx.barbell_graph(m1, m2)
      assert is_isomorphic(b, nx.path_graph(m2 + 4))
  
      pytest.raises(
          nx.NetworkXError,
          nx.barbell_graph,
          m1,
          m2,
          create_using=nx.DiGraph(),
      )
  
      mb = nx.barbell_graph(m1, m2, create_using=nx.MultiGraph())
      assert edges_equal(mb.edges(), b.edges())
  
imports: import itertools
  import typing
  import pytest
  import networkx
  from networkx.algorithms.isomorphism.isomorph import graph_could_be_isomorphic
  from networkx.utils import edges_equal, nodes_equal
label_desc: Use image node_id 9 for calling the TestGeneratorClassic obj's underlying member method code with example usage: obj.test_barbell_graph() without return types