Self is not defined

Here is the stack trace:

Traceback (most recent call last):
   File "V:\Users\Administrator\AppData\Roaming\Blender Foundation\Blender\2.61\scripts\addons\ArenWorldExporter.py", line 73, in execute
     _mkdir(self.filepath[:-4] + "\\models\\")
   File "V:\Users\Administrator\AppData\Roaming\Blender Foundation\Blender\2.61\scripts\addons\ArenWorldExporter.py", line 73, in _mkdir
     _mkdir(self.filepath[:-4] + "\\models\\")
 NameError: global name 'self' is not defined
 

Here is the code:
http://pastebin.com/B2U0DAr8

All the spacing is set to 4 spaces, no tabs (not even sure if the python editor supports tabs)

Why is it saying that self is not defined? As it clearly is in the function.

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