code: def test_shortest_path_length(self):
      assert nx.shortest_path_length(self.cycle, 0, 3) == 3
      assert nx.shortest_path_length(self.grid, 1, 12) == 5
      assert nx.shortest_path_length(self.directed_cycle, 0, 4) == 4
      # now with weights
      assert (
          nx.shortest_path_length(self.cycle, 0, 3, weight="weight")
          == 3
      )
      assert (
          nx.shortest_path_length(self.grid, 1, 12, weight="weight")
          == 5
      )
      assert (
          nx.shortest_path_length(
              self.directed_cycle, 0, 4, weight="weight"
          )
          == 4
      )
      # weights and method specified
      assert (
          nx.shortest_path_length(
              self.cycle, 0, 3, weight="weight", method="dijkstra"
          )
          == 3
      )
      assert (
          nx.shortest_path_length(
              self.cycle, 0, 3, weight="weight", method="bellman-ford"
          )
          == 3
      )
      # confirm bad method rejection
      pytest.raises(
          ValueError, nx.shortest_path_length, self.cycle, method="SPAM"
      )
      # confirm absent source rejection
      pytest.raises(
          nx.NodeNotFound, nx.shortest_path_length, self.cycle, 8
      )
  
imports: import pytest
  import networkx
label_desc: Use image node_id 4 for calling the TestGenericPath obj's underlying member method code with example usage: obj.test_shortest_path_length() without return types