Remove customised memory state when using stategraph

[SalmonSung]

I designed a memory state as following:

class SectionState(TypedDict, total=False):
    orig_file_path: str
    columns_info: str
    code_approval_items: Annotated[list, operator.add]

I'm trying to manipulate(delete) the values in code_approval_items key. However, it always merge two list together...I must use operator.add beacuse this column is collected from a bunch of Send API...

def format_response(state: SectionState, config: RunnableConfig):
    code_approval_items_dict = []
    for item in state["code_approval_items"]:
        code_approval_items_dict.append(pydantic2dict(item))
    if "code_approval_items" in state:
        del state["code_approval_items"]
    state["code_approval_items"] = code_approval_items_dict
    return state

Any clue on how to solve this problem?