title: Function in LuCI project
body: <p>Here is a code block in LuCI (<a href="http://en.wikipedia.org/wiki/OpenWrt" rel="nofollow">OpenWrt</a> web UI) project.</p>
  
  <p>I don't understand what this function is doing, and I am unable to find where it is called. Where is this function being called and what it is doing?</p>
  
  <pre><code>p = s:option(ListValue, "proto", translate("Protocol"))
  p.override_values = true
  
  p:value("pppoe", "PPPoE") 
  p:value("pptp",  "PPTP")  
  
  function p.write(self, section, value)
      if value == "pptp" or value == "pppoe" then
          self.map:set(section, "peerdns", "1")
          self.map:set(section, "defaultroute", "1")
      end
      return ListValue.write(self, section, value)
  end
  </code></pre>