def METHOD_NAME(
        calltree: Optional[CalltreeCallsite]) -> List[CalltreeCallsite]:
    if calltree is None:
        logger.error("Trying to extract from a None calltree")
        raise CalltreeError("Calltree is None")
    cs_list: List[CalltreeCallsite] = []
    extract_all_callsites_recursive(calltree, cs_list)
    return cs_list