AwesomeWM binding to configure positions of Monitors

rc.lua

-- This snippet is a code I wrote to configure the position of monitors with AwesomeWM
-- Usage :
-- Press your Display button (or whatever you binded it to)
-- Popup will show the name of a connected monitor
-- Press an arrow key or Display button to set this monitor in this direction relatively to your main monitor, (display for same position)
-- It will continue until you have configured all connected monitors

-- the name of your main screen as shown in xrandr
main_screen = "eDP1"

-- Helper function to conf a screen
function conf_screen(screen, mode, pos)
   if screen == nil then cmd = "xrandr --auto"
   else
      cmd = "xrandr --output " .. screen .. " --mode " .. mode .. " --" .. pos .. " " .. main_screen
   end
   awful.spawn(cmd)
end

-------------------------------
-- Add this in your  globalkeys

  awful.key({}, "XF86Display",
              function ()
	          -- Command to get list of other screens and best mode
	          -- hack to handle when monitors mode are not sorted, like my TV does.
		  local get_screens = "xrandr | awk '/ connected/{screen=$1;a=1;next}/connected/{a=0}a{print screen \" \" $1}' | sort -k2n | tac | sort -u -k1,1 | grep -v " .. main_screen
		  awful.spawn.easy_async_with_shell(get_screens,
		       function(stdout, stderr, reason, exit_code)

			   -- Process the results
			   screens = {}
			   for i in stdout:gmatch("[^\r\n]+") do
			      a, b = i:match("(%S+) (%S+)")
			      table.insert(screens, {a, b})
			   end

			   -- If no screens, reset conf
			   if #screens == 0 then conf_screen(); return end

			   -- For each screens, ask position
			   local idx = 1
			   local notif = naughty.notify { text = "Position for " .. screens[idx][1] }
			   local grabber 
                           grabber = awful.keygrabber.run(function(mod, key, event)
				 if event == "release" then return end

				 if key == "XF86Display" then conf_screen(screens[idx][1], screens[idx][2], "same-as")
				 elseif key == 'Up'      then conf_screen(screens[idx][1], screens[idx][2], "above")
				 elseif key == 'Down'    then conf_screen(screens[idx][1], screens[idx][2], "below")
				 elseif key == 'Right'   then conf_screen(screens[idx][1], screens[idx][2], "right-of")
				 elseif key == 'Left'    then conf_screen(screens[idx][1], screens[idx][2], "left-of")
				 else return
				 end

				 if idx < #screens then
 				     idx = idx + 1
				     naughty.destroy(notif)
				     notif = naughty.notify { text = "Position for " .. screens[idx][1] }
				 else
 				     naughty.destroy(notif)
				     awful.keygrabber.stop(grabber)
				 end
			   end)
		  end)
	      end,
	      {description = "Display management auto", group = "function keys"})

Where's that top bit of the code meant to go?

main_screen = "eDP1"

-- Helper function to conf a screen
function conf_screen(screen, mode, pos)
   if screen == nil then cmd = "xrandr --auto"
   else
      cmd = "xrandr --output " .. screen .. " --mode " .. mode .. " --" .. pos .. " " .. main_screen
   end
   awful.spawn(cmd)
end