<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def disable_site(site_name):
 """Disables Nginx site configuration."""


    site = u'/etc/nginx/sites-enabled/%s' % site_name
    if files.exists(site):
        sudo(u'rm %s' % site)
        restart_service(u'nginx')