code: def test_is_fit(shadow_dec_tree: ShadowLightGBMTree):
      assert shadow_dec_tree.is_fit() is True
  
file_path: dtreeviz/testing/testlib/models/test_decision_tree_lightgbm_classifier.py
imports: import lightgbm
  import pytest
  from dtreeviz.models.lightgbm_decision_tree import ShadowLightGBMTree
  import numpy
label_desc: Use image node_id 3 for calling a global function with example usage: test_is_fit(shadow_dec_tree) without return types