Add delete for object_set_dict

vm/src/builtins/object.rs

@@ -495,9 +495,17 @@ pub fn object_get_dict(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyDict
     obj.dict()
         .ok_or_else(|| vm.new_attribute_error("This object has no __dict__".to_owned()))
 }
-pub fn object_set_dict(obj: PyObjectRef, dict: PyDictRef, vm: &VirtualMachine) -> PyResult<()> {
-    obj.set_dict(dict)
-        .map_err(|_| vm.new_attribute_error("This object has no __dict__".to_owned()))
+pub fn object_set_dict(obj: PyObjectRef, dict: PySetterValue<PyDictRef>, vm: &VirtualMachine) -> PyResult<()> {
+    match dict {
+        PySetterValue::Some(dict) => {
+            obj.set_dict(dict)
+                .map_err(|_| vm.new_attribute_error("This object has no __dict__".to_owned()))
+        }
+        PySetterValue::None => {
+            obj.delete_dict()
+                .map_err(|_| vm.new_attribute_error("This object has no deletable __dict__".to_owned()))
+        }
+    }
 }
 
 pub fn init(ctx: &Context) {