'_ is not part of the string library' Error... When it should be...

[Defton]

So I have been working on this code for a long time. It is a HEAVY modification to a leveling system that was already created. The back end is basically all remodelled at this point. Anyway, I am almost done but there is this one error that occurs. The code cannot seem to update the variables for the experience points because of this error:

[ERROR] gamemodes/falloutunlimited/plugins/levelup/sh_plugin.lua:234: attempt to index a string value with bad key ('levelup' is not part of the string library)
1. error - [C]:-1
   2. __index - lua/includes/extensions/string.lua:301
    3. increaseExperience - gamemodes/falloutunlimited/plugins/levelup/sh_plugin.lua:234
     4. onRun - gamemodes/falloutunlimited/plugins/levelup/sh_plugin.lua:183
      5. run - gamemodes/nutscript/gamemode/core/libs/sh_command.lua:145
       6. parse - gamemodes/nutscript/gamemode/core/libs/sh_command.lua:180
        7. Run - gamemodes/nutscript/gamemode/core/hooks/sv_hooks.lua:248
         8. unknown - gamemodes/nutscript/plugins/chatbox/sh_plugin.lua:69
          9. func - gamemodes/nutscript/gamemode/core/libs/thirdparty/sh_netstream2.lua:117
           10. unknown - lua/includes/extensions/net.lua:32

Here is the code of the Function that actually increases the experience points:

	//THIS IS WHAT INCREASES THE EXPERIENCE
	function levelup.increaseExperience( ply, amount )
		if not ply.levelup then print("There is no ply.levelup "..ply) return end
		ply.levelup.experience = ply.levelup.experience + amount
		levelup.hud.addNote( ply, "Experience awarded! +" .. amount .. " EXP", Color( 205, 255, 0 ) )
		print("I Made it Into Here!")
		if levelup.hasEnoughExperience( ply, levelup.config.expPerLevel * ( levelup.getLevel( ply ) + 1 ) ) then
			ply.levelup.level = ply.levelup.level + 1
			ply.levelup.experience = 0
			levelup.useEventPerks( ply )
			levelup.hud.addNote( ply, "Level up! You are now on level: " .. ply.levelup.level, Color( 205, 255, 0 ) )
		end
		levelup.database.save( ply, ply:getChar():getID() )
		levelup.sendData( ply )
	end

I have been at this for hours but I can't seem to figure it out :I Some support would be greatly appreciated. I obviously have player initualization code that sets up the 'ply.levelup' table and the the subsequent coulmns level and experience. Maybe I'm missing somethng? Also if you need more code for context, let me know. Thanks.

[sannys]

The ply variable is a string.

[Defton]

[QUOTE=sannys;51584707]The ply variable is a string.[/QUOTE]

... oh my god... You are so right... I'm sorry I'm tired out of my mind.