code: def test_object_delitem_delegated():
      """Delegation in __delitem__ works"""
  
      class ThingDelegate:
          def __init__(self, value):
              self.value = value
  
      class Thing(Object):
          _delegated_properties = ["value"]
  
          def __init__(self, value=None, **data):
              self._delegate = ThingDelegate(value)
              super().__init__(**data)
  
      thing = Thing(1)
      assert thing["value"] == 1
      with pytest.warns(FionaDeprecationWarning, match="immutable"):
          del thing["value"]
      assert thing["value"] is None
  
imports: import pytest
  from fiona.errors import FionaDeprecationWarning
  from fiona.model import _Geometry, Feature, Geometry, Object, ObjectEncoder, Properties, decode_object
label_desc: Use image node_id 8 for calling a global function with example usage: test_object_delitem_delegated() without return types