docstr: Group degree centrality for group with more than
  1 node
docstr_tok: ["Group","degree","centrality","for","group","with","more","than","1","node"]
code: def test_group_degree_centrality_multiple_node(self):
      """
      Group degree centrality for group with more than
      1 node
      """
      G = nx.Graph()
      G.add_nodes_from([1, 2, 3, 4, 5, 6, 7, 8])
      G.add_edges_from(
          [
              (1, 2),
              (1, 3),
              (1, 6),
              (1, 7),
              (1, 8),
              (2, 3),
              (2, 4),
              (2, 5),
          ]
      )
      d = nx.group_degree_centrality(G, [1, 2])
      d_answer = 1
      assert d == d_answer
  
imports: import pytest
  import networkx
label_desc: Use image node_id 2 for calling the TestGroupDegreeCentrality obj's underlying member method code with example usage: obj.test_group_degree_centrality_multiple_node() without return types