human
Solve the following python programming problem given the following code:
@utils.arg('--start', metavar='<start>', help=_('Usage    range    start    date    ex    2012-01-20.    (default:    4    weeks    ago)'), default=None)
@utils.arg('--end', metavar='<end>', help=_('Usage    range    end    date,    ex    2012-01-20.    (default:    tomorrow)'), default=None)
@utils.arg('--tenant', metavar='<tenant-id>', default=None, help=_('UUID    of    tenant    to    get    usage    for.'))
def do_usage(cs, args):
assistant
#Here is the Python code you requested.

    """Show usage data for a single tenant.
    """
    dateformat = '%Y-%m-%d'
    rows = ['Servers', 'RAM    MB-Hours', 'CPU    Hours', 'Disk    GB-Hours']
    now = timeutils.utcnow()
    if args.start:
        start = datetime.datetime.strptime(args.start, dateformat)
    else:
        start = (now - datetime.timedelta(weeks=4))
    if args.end:
        end = datetime.datetime.strptime(args.end, dateformat)
    else:
        end = (now + datetime.timedelta(days=1))
    def simplify_usage(u):
        simplerows = [x.lower().replace('    ', '_') for x in rows]
        setattr(u, simplerows[0], ('%d' % len(u.server_usages)))
        setattr(u, simplerows[1], ('%.2f' % u.total_memory_mb_usage))
        setattr(u, simplerows[2], ('%.2f' % u.total_vcpus_usage))
        setattr(u, simplerows[3], ('%.2f' % u.total_local_gb_usage))
    if args.tenant:
        tenant_id = args.tenant
    elif isinstance(cs.client, client.SessionClient):
        auth = cs.client.auth
        tenant_id = auth.get_auth_ref(cs.client.session).project_id
    else:
        tenant_id = cs.client.tenant_id
    if (cs.api_version < api_versions.APIVersion('2.40')):
        usage = cs.usage.get(tenant_id, start, end)
    else:
        usage = cs.usage.get(tenant_id, start, end)
        marker = _get_usage_marker(usage)
        while marker:
            next_usage = cs.usage.get(tenant_id, start, end, marker=marker)
            marker = _get_usage_marker(next_usage)
            if marker:
                _merge_usage(usage, next_usage)
    print((_('Usage    from    %(start)s    to    %(end)s:') % {'start': start.strftime(dateformat), 'end': end.strftime(dateformat)}))
    if getattr(usage, 'total_vcpus_usage', None):
        simplify_usage(usage)
        utils.print_list([usage], rows)
    else:
        print(_('None'))