code: def test_parameters_add_with_symtable():
      """Regression test for GitHub Issue 607."""
      pars1 = lmfit.Parameters()
      pars1.add("a", value=1.0)
  
      def half(x):
          return 0.5 * x
  
      pars2 = lmfit.Parameters(usersyms={"half": half})
      pars2.add("b", value=3.0)
      pars2.add("c", expr="half(b)")
  
      params = pars1 + pars2
      assert_allclose(params["c"].value, 1.5)
  
      params = pars2 + pars1
      assert_allclose(params["c"].value, 1.5)
  
      params = deepcopy(pars1)
      params.update(pars2)
      assert_allclose(params["c"].value, 1.5)
  
      pars1 += pars2
      assert_allclose(params["c"].value, 1.5)
  
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 12 for calling a global function with example usage: test_parameters_add_with_symtable() and returns: unknown