def METHOD_NAME(state: TreeStateDict) -> None:
    """Called at the beginning of article processing"""
    session = state["session"]  # Database session
    url = state["url"]  # URL of the article being processed
    # Delete all existing locations for this article
    session.execute(Location.table().delete().where(Location.article_url == url))  # type: ignore
    # Set that will contain all unique locations found in the article
    state["locations"] = set()