code: def test_tol_init_param(tol):
      sel = DropConstantFeatures(tol=tol)
      assert sel.tol == tol
  
file_path: feature_engine/tests/test_selection/test_drop_constant_features.py
imports: import numpy
  import pandas
  import pytest
  from feature_engine.selection import DropConstantFeatures
label_desc: Use image node_id 6 for calling a global function with example usage: test_tol_init_param(tol) without return types