code: def test_parameter_set_expr(parameter):
      """Test the Parameter.set() function with expr.
  
      Of note, this only tests for setting/removal of the expression; nothing
      else gets evaluated here... More specific tests that require a Parameters
      class can be found below.
  
      """
      par, _ = parameter
  
      par.set(expr="2.0*50.0")  # setting an expression, vary --> False
      changed_attribute_values = (
          "a",
          10.0,
          False,
          -100.0,
          100.0,
          "2.0*50.0",
          5.0,
          1,
      )
      assert_parameter_attributes(par, changed_attribute_values)
  
      par.set(expr=None)  # nothing should change
      assert_parameter_attributes(par, changed_attribute_values)
  
      par.set(expr="")  # should remove the expression
      changed_attribute_values = (
          "a",
          10.0,
          False,
          -100.0,
          100.0,
          None,
          5.0,
          1,
      )
      assert_parameter_attributes(par, changed_attribute_values)
  
imports: from math import trunc
  import pickle
  import numpy
  from numpy.testing import assert_allclose
  import pytest
  import lmfit
label_desc: Use image node_id 11 for calling a global function with example usage: test_parameter_set_expr(parameter) without return types