def break_clusters(entrez_records: dict, guaranteed: list) ->None:
    """
    Sets the `cluster_rep` variable to True for each EntrezRecord with its num_id found in guaranteed.

    :param entrez_records: Dictionary mapping unique TreeSAPP numerical IDs to Cluster instances
    :param guaranteed: List of sequences to be set to cluster representatives to ensure they are retained downstream
    :return: None
    """
    for num_id in entrez_records:
        if num_id in guaranteed:
            er = entrez_records[num_id]
            er.cluster_rep = True
    return
