http://docs.python.org/py3k/tutorial/classes.html#random-remarks
> Methods may reference global names in the same way as ordinary
> functions. The global scope associated with a method is the module
> containing the class definition. (The class itself is never used
> as a global scope.)

Method's function can be defined outside the module containing class
definition. And then the method's global scope is module containing
method's function definition.