code: def test_add_params_expr_outoforder():
      """Regression test for GitHub Issue 560."""
      params1 = lmfit.Parameters()
      params1.add("a", value=1.0)
  
      params2 = lmfit.Parameters()
      params2.add("b", value=1.0)
      params2.add("c", value=2.0)
      params2["b"].expr = "c/2"
  
      params = params1 + params2
      assert "b" in params
      assert_allclose(params["b"].value, 1.0)
  
imports: from copy import copy, deepcopy
  import os
  import pickle
  import numpy
  from numpy.testing import assert_allclose
  import pytest
  import lmfit
  from lmfit.models import VoigtModel
label_desc: Use image node_id 22 for calling a global function with example usage: test_add_params_expr_outoforder() without return types