How do I use the unittest setUpClass method()?

I'm looking for some basic examples of the python 2.7 unittest setUpClass() method. I'm trying to test some class methods in my module, and I've gotten as far as:

import unittest  
import sys  

import mymodule  

class BookTests(unittest.TestCase):  
    @classmethod  
    def setUpClass(cls):  
        cls._mine = mymodule.myclass('test_file.txt', 'baz')  

But I have no idea how to proceed from here to write tests utilising the object I just created.