def METHOD_NAME(previous_dir, csv_name):
    '''
    return a set of hashes for rows in previous_dir/filtered/csv_name,
    excluding the organization fields to avoid counting org changes
    as row changes
    '''
    existing = set()
    with open(Path(previous_dir, 'filtered', csv_name)) as f:
        csv = DictReader(f)
        for row in csv:
            del row['owner_org']
            del row['owner_org_title']
            existing.add(
                hashlib.md5(repr(list(row.values())).encode('utf8')).digest()
            )
    return existing