code: def test_get_lineage_existing_root_trial(self):
      lineages = Lineages()
      trial = TrialStub(id="stub")
      lineage = lineages.add(trial)
      assert lineages.get_lineage(trial) is lineage
  
imports: import os
  import random
  import pytest
  from base import ObjectiveStub, TrialStub, build_full_tree, build_population, compare_generations
  from orion.algo.pbt.pbt import LineageNode, Lineages
label_desc: Use image node_id 5 for calling the TestLineages obj's underlying member method code with example usage: obj.test_get_lineage_existing_root_trial() without return types