code: def test_depth():
      text = "(foo) ((S (VP (VB Unban)) (NP (NNP Mox) (NNP Opal))))"
      trees = tree_reader.read_trees(text)
      assert trees[0].depth() == 0
      assert trees[1].depth() == 4
  
imports: import pytest
  from stanza.models.constituency.parse_tree import Tree
  from stanza.models.constituency import tree_reader
  from stanza.tests import *
label_desc: Use image node_id 3 for calling a global function with example usage: test_depth() without return types