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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 cli(env, sortby, cpu, domain, datacenter, hostname, memory, network, hourly, monthly, tag, columns, limit):
 """List virtual servers."""


    vsi = SoftLayer.VSManager(env.client)
    guests = vsi.list_instances(hourly=hourly,
                                monthly=monthly,
                                hostname=hostname,
                                domain=domain,
                                cpus=cpu,
                                memory=memory,
                                datacenter=datacenter,
                                nic_speed=network,
                                tags=tag,
                                mask=columns.mask(),
                                limit=limit)

    table = formatting.Table(columns.columns)
    table.sortby = sortby
    for guest in guests:
        table.add_row([value or formatting.blank()
                       for value in columns.row(guest)])

    env.fout(table)