Google AppEngine: How to fetch more than 1000 entities?

def fetch_all(query, max_entries=1000):
    ''' fetch all entities '''
    entries = []
    
    count = 0
    query = query.order('__key__')
    while count % max_entries == 0:
        items = query.fetch(max_entries)
        for i, item in enumerate(items):
            entry = {}
            entry['gae_key'] = str(item.key())
            for field in item.fields(): entry[field] = getattr(item, field)
            entries.append(entry)
                            
        current_count = len(items)
        count += current_count

        if current_count == max_entries:
            last_key = query.fetch(1, max_entries-1)[0].key()
            query = query.filter('__key__ > ', last_key)
    return entries