def get_categories_in_feather(nhd_cats, columns):
    """
    get a filtered set of columns in a dataframe. the filter is a list of nhd 
    catchment attributes that we are interested in. if none of the columns are
    in the attributes that we are interested in, it will return an empty index
    :param nhd_cats: [list] list of nhd attributes that we are interested in
    :param columns: [pandas index] a pandas index of the columns that we are 
    potentially interested in
    :return: [pandas index] a pandas index with the columns that are in the nhd
    catchment attributes that we are interested in
    """
    in_cats = columns[columns.isin(nhd_cats)]
    return in_cats