code: def __init__(self):
      super().__init__()
      self.mixed_left = SimpleFlowTree()
      self.work_tree = SimpleWorkTree()
      self.mixed_right = SimpleFlowTree()
  
file_path: pytorch-lightning/tests/tests_app/utilities/test_tree.py
imports: import pytest
  from lightning.app import LightningFlow, LightningWork
  from lightning.app.testing.helpers import EmptyFlow, EmptyWork
  from lightning.app.utilities.tree import breadth_first
label_desc: Use image node_id 1 to create a new MixedTree object from inherited base classes: EmptyFlow with example: obj = MixedTree()