code: def test_variable_names(self):
      space = [
          {
              "name": "var1",
              "type": "continuous",
              "domain": (-1, 1),
              "dimensionality": 2,
          },
          {
              "name": "var2",
              "type": "categorical",
              "domain": ("r", "g", "b"),
              "dimensionality": 3,
          },
          {
              "name": "var3",
              "type": "discrete",
              "domain": (0, 1, 2, 3),
              "dimensionality": 2,
          },
          {"name": "var4", "type": "continuous", "domain": (-1, 1)},
          {
              "name": "var5",
              "type": "continuous",
              "domain": (-1, 1),
              "dimensionality": 1,
          },
      ]
  
      design_space = Design_space(space)
  
      var_names = [
          "var1_1",
          "var1_2",
          "var2_1",
          "var2_2",
          "var2_3",
          "var3_1",
          "var3_2",
          "var4",
          "var5",
      ]
  
      k = 0
      for variable in design_space.space_expanded:
          self.assertTrue(variable.name == var_names[k])
          k += 1
  
imports: import numpy
  import unittest
  from GPyOpt.core.task.space import Design_space
  from GPyOpt.core.task.variables import BanditVariable, DiscreteVariable, CategoricalVariable, ContinuousVariable
  from GPyOpt.core.errors import InvalidConfigError
label_desc: Use image node_id 19 for calling the TestDesignSpace obj's underlying member method code with example usage: obj.test_variable_names() without return types