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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def get_ladder(session, ladder_id, user_id=None, user_ids=None, start=0, limit=LADDER_RESULT_LIMIT):
 """Get ladder."""

    params = {
        'start': start,
        'limit': limit
    }
    if isinstance(ladder_id, str):
        ladder_id = lookup_ladder_id(ladder_id)
    if limit > LADDER_RESULT_LIMIT:
        raise VooblyError('limited to 40 rows')
    if user_ids:
        params['uidlist'] = ','.join([str(uid) for uid in user_ids])
    elif user_id:
        params['uid'] = user_id
    resp = _make_request(session, LADDER_URL, ladder_id, params)
    if user_id:
        if not resp:
            raise VooblyError('user not ranked')
        return resp[0]
    return resp