code: def test_model_space_no_label_prefix(caplog):
      class ModelSpace1(ModelSpace, label_prefix=""):
          pass
  
      with pytest.raises(ValueError, match="be empty"):
          ModelSpace1()
  
      class ModelSpace2(ModelSpace):
          def __init__(self):
              super().__init__()
              self.a = self.add_mutable(
                  Categorical([1, 2, 3], label="a")
              )
              assert self.a.label == "a"
              with pytest.raises(ValueError, match="must be specified"):
                  self.b = self.add_mutable(Categorical([1, 2, 3]))
  
      ModelSpace2()
  
      class ModelSpace3(ModelSpace):
          def __init__(self):
              super().__init__()
              self.a = self.add_mutable(
                  Categorical([1, 2, 3], label="a")
              )
              assert self.a.label == "model4/a"
              with pytest.raises(ValueError, match="must be specified"):
                  self.b = self.add_mutable(Categorical([1, 2, 3]))
  
      class ModelSpace4(ModelSpace, label_prefix="model4"):
          def __init__(self):
              super().__init__()
              ModelSpace3()
              self.a = self.add_mutable(
                  Categorical([1, 2, 3], label="a")
              )
              assert self.a.label == "model4/a"
              self.b = self.add_mutable(Categorical([1, 2, 3]))
              assert self.b.label == "model4/1"
  
      class ModelSpace5(ModelSpace):
          def __init__(self):
              super().__init__()
              ModelSpace4()
  
      ModelSpace5()
  
imports: import copy
  import pytest
  import torch
  import nni
  from torch import nn
  from nni.common.serializer import is_traceable
  from nni.mutable import Categorical, ExpressionConstraint, ensure_frozen, frozen_context, label_scope, auto_label, SampleMissingError
  from nni.mutable.mutable import _mutable_equal
  from nni.nas.nn.pytorch import ModelSpace, MutableModule, ParametrizedModule
  from nni.nas.space import model_context
label_desc: Use image node_id 14 for calling a global function with example usage: test_model_space_no_label_prefix(caplog) without return types