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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 list_queues(region, opts=None, user=None):
    '''
    List the queues in the selected region.

    region
        Region to list SQS queues for

    opts : None
        Any additional options to add to the command line

    user : None
        Run hg as a user other than what the minion runs as

    CLI Example:

        salt '*' aws_sqs.list_queues <region>

    '''
    out = _run_aws('list-queues', region, opts, user)

    ret = {
        'retcode': 0,
        'stdout': out['QueueUrls'],
    }
    return ret