[jQuery] help writing first plugin

[Liam Potter]

Hi Guys,
http://jsbin.com/ebidu/edit#javascript

I'm writing a plugin to help make styling forms and doing certain common 
tricks with them.

I'm running into trouble when I try and put parts into functions.

you can see at jsbin I have a function called labelInside, but I can't 
use this.children to get to the label, I have to target it directly, 
which means I can run the plugin like this

<script>
$(function () {
           $("form.that_doesn't_exist").jform({
                           labelInside: true
                           });
           });
</script>

so long as labelInside is true that function will run, and because I 
have targeted labels directly it runs anyways.

How would I go about making this function only run on the specified element?

- Liam