code: def test_categorical_slot_ignores_none_value():
      """Checks that None can't be added as a possible value for categorical slots."""
      with pytest.warns(UserWarning) as records:
          slot = CategoricalSlot(
              name="branch",
              mappings=[{}],
              values=["Berlin", None, "San Francisco"],
          )
  
      assert "none" not in slot.values
  
      message_text = "Rasa will ignore `null` as a possible value for the 'branch' slot."
      assert any(
          message_text in record.message.args[0] for record in records
      )
  
imports: from typing import Any, Tuple, List, Dict, Text
  import pytest
  from _pytest.fixtures import SubRequest
  import rasa.shared.core.constants
  from rasa.shared.core.events import SlotSet
  from rasa.shared.core.slots import InvalidSlotTypeException, Slot, TextSlot, BooleanSlot, FloatSlot, ListSlot, CategoricalSlot, bool_from_any, AnySlot, InvalidSlotConfigError
  from rasa.shared.core.trackers import DialogueStateTracker
label_desc: Use image node_id 4 for calling a global function with example usage: test_categorical_slot_ignores_none_value() without return types