def string_to_list(string_df, column_1='ID', column_2='ID_0'):
    """Convert AdH Boundary String dataframe into a list of properly ordered nodes
    AdH Boundary Strings are 2 column format, each row consists of two nodes that make
    up one edge. The second node is repeated as the first node on the next row

    Args:
        string_df: dataframe
            Boundary string dataframe (already reduced to a single string)
        column_1: string
            Dataframe column label of the first vertex of the edge
        column_2: string
            Dataframe column label for the second vertex of the edge

    Returns:
        Boundary string nodes as a list

    """
    # get the string series as a list
    lst = string_df[column_1].to_list()
    # add the last node in the string
    lst.append(string_df[column_2].iloc[-1])
    # return the list
    return lst