Method add_done_callback

crates/stdlib/src/_asyncio.rs:333–362

(
            zelf: PyRef<Self>,
            args: AddDoneCallbackArgs,
            vm: &VirtualMachine,
        )

        #[pymethod]
        fn add_done_callback(
            zelf: PyRef<Self>,
            args: AddDoneCallbackArgs,
            vm: &VirtualMachine,
        ) -> PyResult<()> {
            if zelf.fut_loop.read().is_none() {
                return Err(vm.new_runtime_error("Future object is not initialized."));
            }
            let ctx = match args.context.flatten() {
                Some(c) => c,
                None => get_copy_context(vm)?,
            };

            if zelf.fut_state.load() != FutureState::Pending {
                Self::call_soon_with_context(&zelf, args.func, Some(ctx), vm)?;
            } else if zelf.fut_callback0.read().is_none() {
                *zelf.fut_callback0.write() = Some(args.func);
                *zelf.fut_context0.write() = Some(ctx);
            } else {
                let tuple = vm.ctx.new_tuple(vec![args.func, ctx]);
                let mut callbacks = zelf.fut_callbacks.write();
                if callbacks.is_none() {
                    *callbacks = Some(vm.ctx.new_list(vec![tuple.into()]).into());
                } else {
                    let list = callbacks.as_ref().unwrap();
                    vm.call_method(list, "append", (tuple,))?;
                }
            }
            Ok(())
        }

        #[pymethod]
        fn remove_done_callback(&self, func: PyObjectRef, vm: &VirtualMachine) -> PyResult<usize> {